Passivhaus Tenement

Potential of Affordable Multi-family Passivhaus Housing in Urban Glasgow

The Case of Pre-fabricated Massive Timber Construction

A Research Project by:

Lilija Oblecova

Submitted for:

Bachelor of Architecture (Honours)

Mackintosh School of Architecture

Glasgow School of Art

April 2012

Acknowledgements

I am sincerely grateful to my research project supervisor, Dr. Filbert Musau,

for his insightful advice throughout the course of the project. My thankfulness

extends also to Alexander Romanov for his knowledgeable comments and

continuing encouragement.

Contents

List of Illustrations

List of Abbreviations

Executive Summary

Introduction

1. Context

1.1. Affordable Housing in Glasgow

1.1.1. Affordable Housing Typologies ....................................... 8

1.1.2. Affordable Housing Provision Trends ............................ 12

1.2. Sustainable Housing

1.2.1. Scotland: Standards and Codes .................................... 17

1.2.2. Passivhaus Standard

1.2.2.1. Requirements / Definition .................................. 20

1.2.2.2. Applicability to the Tenement ............................. 22

1.2.2.3. Passivhaus in the UK ......................................... 24

2. Construction

2.1. Timber Construction

2.1.1. Advantages ................................................................ 26

2.1.2. Timber Construction in Scotland ................................... 27

2.3. Modern Methods of Timber Construction

2.2.1. Applicability to Affordable Housing ............................... 28

2.3.1. Engineered timber: Cross-Laminated Panels

2.3.1.1. Properties and Features .................................... 30

2.3.1.2. Suitability for Passivhaus Construction................. 32

2.3.1.3. Procurement .................................................... 33

3. Case Studies

3.1. Mühlweg Street, Vienna, Dietrich I Untertrifaller Architekten, 2006

3.1.1. Background to the Project ........................................... 35

3.1.2. Construction ............................................................... 37

3.1.3. Environmental Systems and Performance ..................... 38

3.2. Passivhaus and Massive Timber in the UK ............................... 39

3.3. Conclusions .......................................................................... 43

4. Simulation

4.1. Description of Method & Scenarios

4.1.1. Method ...................................................................... 45

4.1.2. Scenarios 1 & 2 - Original & Refurbished Tenements ..... 50

4.1.3. Scenario 3 - Building Standards + CLT .......................... 51

4.1.4. Scenario 4 - Building Standards + CLT + Passivhaus ..... 53

4.2. Simulation Results and Analysis

4.2.1. Compliance Check ...................................................... 56

4.2.2. Specific Annual Heating Demand .................................. 59

4.2.3. Effect of Urban Configurations

4.2.4.1. Effect of Terracing ............................................ 63

4.2.4.2. Effect of Hillside Terracing ................................. 64

5. Discussion ................................................................................ 65

Appendices

Bibliography

1

List of Illustrations*

Fig.1. Plan of a typical tenement ........................................................... 8 Fig.2. Map of Glasgow showing the ratio of dwellings to the acre (height represents density) and tenure profile of dwellings (2008) by neighbourhoods ....................................... 16 Fig.3. Cross-Laminated Timber panel: pre-fabricated, fire resistant, air-tight .................................................... 30 Fig.4. External view of Mühlweg Street housing ..................................... 35 Fig.5. Typical Plan of Mühlweg Street housing ....................................... 36 Fig.6. Detail of exterior wall of Mühlweg Street housing ......................... 37 Fig.7. External view of Nash Terrace .................................................... 39 Fig.8. Model of the completed CLT shell of Bridport House ..................... 40 Fig.9. Perspective section through the Stadthaus ................................... 41 Fig.10. Diagram of a typical tenement with assumed external dimensions ............................................................... 46 Fig.11. Diagram of the thermal envelope modelled in this study ............. 47 Fig.12. Achieving Building Standards compliance in the worst case scenario: DER, TER and % Reduction .............................. 52 Fig.13. Effect of terracing on PH compliance of a tenement designed to guideline specifications ..................................... 53 Fig.14. Development of Passivhaus-compliant prototype using PHPP ........................................................................... 54 Fig.15. Dwelling Emission Rate (DER), Target Emission Rate (TER) and % Reduction ........................................ 56 Fig.16. Total CO2 Emissions Equivalent (no household applications) – comparison of SAP (DER) and PHPP results ...................... 57 Fig.17. Heat Loss Parameter and EcoHomes Ene 2 Credits (based on SAP calculations) .................................................................. 58

2

Fig.18. Specific Annual Space Heating Demand and Fabric Energy Efficiency (Comparison of SAP and PHPP results) ............. 59 Fig.19. Specific Annual Space Heating Demand Variations (per flat type as modelled in SAP) ....................................................... 60 Fig.20. Specific Annual Space Heating and Auxiliary Electricity Demand (comparison of SAP and PHPP) .............................. 61 Fig.21. Difference in Specific Annual Heating Demand Depending on Orientation and Street Width (based on PHPP results ...................... 62 Fig.22. Effect of terracing on the performance of PH Tenement (as modelled in PHPP) .................................................. 63 Fig.23. Effect of hillside terracing on the performance of PH Tenement (as modelled in PHPP) .............................................. 64

* The source of illustrations is acknowledged in the text.

3

List of Abbreviations

BRE Building Research Establishment

CLT Cross-laminated timber

DER Dwelling Emission Rate

FEES Fabric Energy Efficiency Standard

GHA Glasgow Housing Association

LZCGT Low and zero carbon generating technology

MMC Modern Methods of Construction

MVHR Mechanical Ventilation with Heat Recovery

PH Passivhaus or Passive House

PHPP Passive House Planning Package

SAP Standard Assessment Procedure

TER Target Emission Rate

4

Executive Summary

Focus

The focus of this project was to test the hypothesis that housing constructed

to the Passivhaus standard from pre-fabricated massive timber panels and

taking precedent from the Glasgow tenement in its urban form is a suitable

affordable housing prototype for Glasgow in terms of construction feasibility

and environmental performance.

Context

The hypothetical Passivhaus Tenement was tested against the climatic, social

and economic conditions found in Glasgow, including a range of applicable

policies.

Pre-fabricated massive timber construction was chosen for its potential to be

manufactured in Scotland and quick erection on site.

Passivhaus is a proven standard that provides a good starting point for

achieving zero-carbon buildings through the adoption of a fabric-first

approach, while also dramatically reducing operational costs.

5

Significance

The research project was triggered by the recognition of the necessity to

develop feasible and publicly attractive alternatives to suburban living

because the latter is unsustainable its use of resources and is contrary to the

principles of green urbanism. 1 This study examines whether multi-storey

timber tenements constructed to the Passivhaus standard could provide

affordable accommodation for the growing number of households in Glasgow

without advanced component specification.

Method

A brief historical overview of housing typologies in Glasgow is followed by an

analysis of Glasgow's affordable housing provision trends, drawing a

connection between areas with identified housing need, density and

traditional tenement districts. Legislative context applicable to sustainable

housing is described, and advantages of Passivhaus are outlined, together

with obstacles to the standard’s adoption in the UK.

An overview of massive timber construction focuses on its suitability for low-

energy multi-storey housing and highlights the material’s sustainability.

1 Lehmann, S., The Principles of Green Urbanism. Regenerating the Post-Industrial City,

(Earthscan, London 2010)

6

An example of a successful scheme is presented, which is social housing on

Mühlweg Street in Vienna by Dietrich I Untertrifaller Architekten. Several case

studies in the UK are also analysed to assess feasibility.

Passive House Planning Package (PHPP) was used to establish that a

detached north-facing tenement constructed to minimum specifications would

not be Passivhaus-compliant in overshadowed conditions. To ensure that the

proposed prototype retains the adaptability of its traditional predecessor, the

components were upgraded to ensure performance in the worst-case scenario.

The prototype’s energy demands were compared to several alternatives. All

sharing the same exterior dimensions, the original and refurbished tenements,

Building Standards version and the prototype Passivhaus – were modelled in

PHPP and FSAP 2009 to obtain comparable figures. The prototype was further

evaluated in terms of the effect of orientation, overshadowing and terracing.

Contribution

The research demonstrates the suitability of cross-laminated timber for the

use as the primary construction material for multi-storey Passivhaus housing.

An insight is provided into the advantages and possible obstacles to adopting

the Passivhaus Tenement prototype as Glasgow’s affordable housing model

for the future.

7

Introduction

Passivhaus Tenement is an adaptable housing unit that can fill the gaps in the

fabric of the city, increasing the density and attractiveness of existing

neighbourhoods. It can provide accommodation that takes into account the

needs of the growing proportion of small households and that is affordable in

that it costs no more than 25% of the household’s chief earner’s income to

rent. 2 It uses a construction system that is quick, sustainable and with

components that could be produced locally. Chapter 1 focuses on the context

in which the prototype is set, and cross-laminated timber construction is

described in Chapter 2. Relevant case studies are presented in Chapter 3.

The prototype is based on Package 1 described in clause 6.1.2 of the Building

Standards (Scotland), but the design was updated to bring the performance

of its components to the standards defined by the Passivhaus Institute. Only

the minimum targets were set, so as to avoid high construction costs.

Whether this yields a working Passive House in the worst case of orientation

and overshadowing and how well it performs in comparison to the

alternatives is investigated in Chapter 4.

2 Paul Balchin and Maureen Rhoden, Housing Policy: An Introduction, 4th Edition, (Routledge,

London, 2002), p.253

8

1. Context

1.1. Affordable Housing in Glasgow 3

1.1.1. Affordable Housing Typologies

A close-knit pattern of vertical flatted housing units has been a common

feature of Scottish urban life from the earliest of times, and Glasgow is no

exception4. The possibility of full and separate ownership of a flat in a block, -

a unique feature of Scots Law, has enabled this typology to flourish and to

develop into the basic housing unit for the working classes - the Glasgow

Tenement. It is a 3-4 storey block with a variety of one- and two-room flats

at each landing (Fig.1).

Fig.1. – Plan of a typical tenement 5

3 The meaning of “affordable” is defined in the Introduction 4 Douglas Niven, The Development of Housing in Scotland, (Croom Helm, London, 1979),

p.22 5 John Gilbert, The Tenement Handbook, (RIAS, Edinburgh, 1993), Fig. 16.1, p.85

9

Before the interest waned in the early 20th century, affordable housing

demand was met by private speculative developers, who used local materials

and subjected the tenement to countless refinements.6 The resulting districts

retain a balanced social mix owing to the strategy of selling land in small plots

to a variety of developers. 7 The ‘way of life’ characteristic to historic

tenements is described in a book by Worsdall.8

In spite of various incentives, private speculation ceased being able to meet

the housing needs of the working classes, so the government had to rise to

the challenge. However, due to the lack of funds, it was forced to reduce

design standards to the bare minimum, resulting in segregated peripheral

developments of ‘dreary boxes’ on Garden City-inspired layouts.9

Housing has been a highly political matter since the 1920s, and the advent of

time-saving pre-fabricated technologies gave it a new force. "Multi" was a

word particularly attractive to politicians and the government introduced a

subsidy for system-built high-rise blocks in blind belief that this typology

would deliver a long-lasting improvement in the quality of life for the

masses.10

6 Niven, p.21 7 Ibid., p.70 8 Worsdall, F., The Tenement : A Way of Life : a Social, Historical and Architectural Study of Housing in Glasgow, (W. and R. Chambers, Edinburgh, 1979) 9 Niven, pp.28,72 10 Ibid., p.76

10

Even though Scotland was numerically unmatched in its public sector housing

provision at the time, 11 public disillusionment came soon after, because

quality was not on the agenda. The main causes of tenants’ dissatisfaction12

could have been eradicated through effective management, but the public

was unwilling to see beyond the surface of deterioration and was led to

believe that 'houses not flats'13 was the way forward.

Unable to find an alternative solution, Scotland launched a vast demolition

programme aimed at the legacy of the high-rise era, which means that the

majority of affected buildings are razed, most likely before having their cost

paid off by the taxpayer.

The density of the high-rise estates as a whole was considerably lower than

traditional tenement districts. It was overcrowding and unsanitary conditions

that should have been tackled, as high density was shown to be beneficial to

the quality of urban life.14 However, by the time it was realised that the

Victorian housing legacy was not devoid of its advantages and redevelopment

was accepted as an alternative to demolition, a lot of the tenements were

already gone.15

11 Ibid., p.34 12 Pearl Jephcott, and Hilary Robinson, Homes in High Flats (Oliver and Boyd, Edinburgh,

1971), [cited in Alice Coleman, Utopia on Trial - Vision and Reality in Planned Housing, (Shipman, London, 1985)]

13 Alice Coleman, Utopia on Trial - Vision and Reality in Planned Housing, (Shipman, London, 1985

14 Jane Jacobs, The Death and Life of Great American Cities, (Modern Library ed., New York, 1993), pp.262-265

15 Niven, p.78

11

The fixed-price contracts typical for public housing procurement meant that

contractors’ profits depended on the absence of delays and low inflation.16

Unwilling to take risks, they turned back to the private sector, producing,

among other things, a number of developments in the tenement tradition,17

verifying that this typology is in demand even with home-owners.

Having a high dwelling/acre ratio, tenement streets can accommodate enough

people to form a basis of a lively community. When supplemented by

additional functions, non-residents start visiting the area, increasing passive

surveillance. Defensible space issues 18 are resolved through a small front

garden demarcated by an iron fence. As a result, typical features of successful

streets are achieved.19 Furthermore, the tenement perimeter block uses urban

resources more intensively compared to suburban alternatives. No matter

how sustainable individual houses are, suburbia encourages further sprawl

and causes pollution through increased transport.20 The majority of theories

concerning sustainable urban design seem to agree on the need for

“decentralised concentration”,21 so it is suggested that Passivhaus Tenements

are added to areas that lack the density to achieve their full potential,

preventing social segregation by the modesty of interventions.

16 Niven, p.108 17 Natalie Marie Trotter, ‘The revival of the tenement tradition in Glasgow’, [Dissertation],

(Mackintosh School of Architecture, Glasgow, 1996) 18 Oscar Newman, Defensible Space: People and Design in the Violent City, (Architectural

Press, London, 1973) 19 Jacobs, p.44 20 Lehmann, p.78 21 Hildebrand Frey, Designing the City. Towards a More Sustainable Urban Form, (Spon Press,

London, 1999), p.39

12

1.1.2. Affordable Housing Provision Trends

In belief that owner occupation was the norm, the Conservative government

introduced the right to buy council housing in 1980, which redistributed

housing resources in the interest of the working class. This, however, led to

wealth accumulation only for the selected few, while others suffered

increasing inequality, leading to problems such as homelessness.22

The coalition of interests that supported the growth of public sector housing

no longer existed and what was left in stock were the least desirable

properties.23 The local authorities acted on the majority vote of their tenants

and transferred all of their remaining stock to housing associations. The latter,

together with a number of Registered Social Landlords currently own around

110,000 properties in Glasgow, which, being 37% of the total stock, is what

constitutes the majority of affordable housing in the city.24

Glasgow’s population is anticipated to rise from 584,240 in 2008 to 614,795 in

2025,25 with number of households projected to increase due to the loss of

families from the city and the ageing population.26

22 John English, (ed.), The Future of Council Housing, (Croom Helm, London, 1982), p.37 23 English, p.36 24 ‘Housing Stock by Tenure for Glasgow's Wards’ (Glasgow City Council, Development &

Regeneration Services, 2011) <http://www.glasgow.gov.uk>, [Accessed on: 4 April 2012] 25 ‘The Development Plan for Glasgow - Main Issues Report’, (Glasgow City Council, 2011)

<http://www.glasgow.gov.uk>, [Accessed on: 11 February 2012], p.11 26 Ibid., p.77

13

The figures representing Glasgow's social rented stock are expected to

decrease from 109,756 in 2008-09 to 96,754 in 2024-25 – which is a 12%

drop.27 This will take Glasgow to the minimum proportion of social housing

that still ensures an effective social mix,28 but it will still have to be supported

by new additions to the stock due to deterioration.

Although these estimated figures are yet to be corroborated through ongoing

work with the Local Housing Strategy, a £410m grant has been made to

housing associations to support the delivery of around 5,400 units.29

Glasgow Housing Association (GHA) is the biggest one in the city. Its aim is to

deliver 750 new homes by 2014 and to support Glasgow's target of cutting its

carbon footprint by 30% by 2020.30 One of the major steps in that direction is

the 'Glasgow House' – family accommodation with a £100 annual heating bill,

which is the first sustainable housing prototype for Glasgow.31 The feasibility

of the project is ensured by involving local suppliers, and most importantly,

City Building, a construction company who are eager to invest time in

developing the skills necessary to achieve the challenging specification.32

27 Ibid., p.43 28 Lehmann, p.221 29 ‘The Development Plan for Glasgow - Main Issues Report’, p.44 30 ‘Our Corporate Strategy. The next three years (2011-2014)’, (Glasgow Housing Association,

2010), p.26 31 Sneddon, J., ‘The Glasgow House - It's Already Happening’, (Glasgow Housing Association,

2010) 32 ‘City Building - Glasgow House Shortlisted for Industry Awards’ , (City Building, 16 May

2011), <http://www.citybuildingglasgow.co.uk/2011/glasgow-house-shortlisted-for-industry-awards/>, [Accessed on: 11 February 2012]

14

Land availability is crucial to providing affordable housing and the Council has

identified ways of optimising the use of this resource. Particular need for

affordable housing has been identified in the West and South of the city, so

releasing greenbelt land is not a solution. An obligation for private housing

developers to provide a portion of affordable homes is believed to become

effective after the economic recovery, and employing some of the land

dedicated to the private sector, e.g. the Community Growth Areas, might be

beneficial in the meantime.33

While new districts require additional investment into infrastructure, urban

infill and post-demolition sites are usually well-serviced and, unless they

require expensive de-contamination, it makes sense for affordable housing to

be constructed there.

The Development Plan discusses urban density policy for its advantages of

creating sustainable communities and attracting investment in local

infrastructure by creating higher demand.34 Although it suggests that higher

densities are mainly appropriate for traditional inner-city locations, it

speculates that densifying locations near important transport nodes outside

the centre would also be advantageous, 35 which is in line with the

“decentralised concentration” discussed earlier.

33 ‘The Development Plan for Glasgow - Main Issues Report’, p.44 34 Ibid., p.45 35 Ibid., p.77

15

The areas with the highest identified need happen to be the densest ones

(Fig.2) and feature traditional tenement districts36. GHA acknowledges the

importance of providing a choice in the type of affordable accommodation

and not just in terms of location, but also typology.37 While there is already

an initiative that deals with sustainable suburban family housing, no

comparable projects have been developed to actually meet the identified

need in the city and to suit the requirements of the growing number of single-

people households. The proposed Passivhaus Tenement is a possible solution

to the problem.

36 McKenna, M., Typology Project: Tenement [A Record of Buildings in Glasgow: Volume One:

October 2011], (Dress for the Weather Limited, SUST, 2011) 37 Glasgow Housing Association: Homechoice, (GHA, 2009),

<https://homechoice.gha.org.uk/>, [Accessed on: 16 February 2012]

16

Fig.2. - Map of Glasgow showing the ratio of dwellings to the acre (height represents density) 38 and tenure profile of dwellings (2008) by neighbourhoods 39

38 Density calculated by the author using Key Facts, (Glasgow City Council, 2010) <http://www.glasgow.gov.uk >, [Accessed on: 18 February 2012] and

housing unit information from Freeke, J., ‘People and Households in Glasgow. Current Estimates and Projected Changes 2008-2028. Demographic Change in Glasgow City and Neighbourhoods’, [Briefing Paper by Director of Development and Regeneration Services, 7 March 2011], (Glasgow City Council, 2011)

39 Adapted from Freeke, p.16

17

1.2. Sustainable Housing

1.2.1. Scotland: Standards and Codes

Around 29% of all energy consumed and 30% of all greenhouse gas

emissions in Scotland derive from the domestic sector. Numerous initiatives

have been supported by the Scottish Government in order to reduce this

impact.40

The main driving force for sustainability in Scottish housing is The Sullivan

Report, which recommended a set of energy improvements on 2007

standards:

30% by 2010 (already incorporated in the Building Standards from

October 2010)

60% by 2013

Net zero carbon by 2016

Total life zero carbon domestic standard by 203041

The latest amendment of the Building Standards featured an introduction of

Section 7 (Sustainability), which further encourages sustainable construction

by introducing three levels – Bronze/Bronze Active, Silver/Silver Active and

Gold. While Bronze Active can be achieved by complying with Sections 1-6

40 ‘Conserve and Save - A Consultation on the Energy Efficiency Action Plan for Scotland’,

(Business, Enterprise and Energy Directorate, Scottish Government, 2009) 41 Sullivan, L., ‘A Low Carbon Building Standards Strategy For Scotland’, [Report of a panel

appointed by Scottish Ministers], (Chaired by Lynne Sullivan from Scottish Building Standards Agency (SBSA), 2007)

18

and utilising low and zero carbon generating technology (LZCGT), the other

levels are more challenging.42

The Climate Change (Scotland) Act requires a 42% reduction in greenhouse

gas emissions by 2020 and 80% by 2050. It also brings amendments to the

Town and Country Planning (Scotland) Act 1997, requiring that all new

buildings minimise their environmental impact through the use of LZCGT.43

A standard imposed on large-scale residential developments in Glasgow is

EcoHomes "Very Good". 44 EcoHomes is a flexible system, which assesses

environmental performance with general lifestyle issues. EcoHomes standard

was replaced by the Code for Sustainable Homes in the rest of the UK in 2007,

together with a set of increasing targets set specifically for social housing.45

A Strategy for Sustainable Housing in Scotland, which is currently being

developed, will tackle energy efficiency issues affecting both new and existing

housing stock.46 Among the difficulties of achieving cost-effective retrofits in

Scotland is a relatively high proportion of flats - 36%.47 Increased costs could

be linked to ownership issues and also the necessity for more complex

42 ‘Building Standards Domestic 2011 Technical Handbook’, (Scottish Government, 2011)

<http://www.scotland.gov.uk/> [Accessed on: 16 March 2012] 43 The Development Plan for Glasgow - Main Issues Report’, 2011, p.80 44 ‘City Plan 2 - Part 3: Development Policies and Design Guidance’, (Glasgow City Council,

2009), <http://www.glasgow.gov.uk/>, [Accessed on: 11 February 2012], p.119 45 ‘BREEAM: EcoHomes’, (Building Research Establishment, 2012) <http://www.breeam.org>,

[Accessed on: 8 April 2012] 46 ‘Conserve and Save - The Energy Efficiency Action Plan for Scotland - Annual Report 2010-

2011’, (Scottish Government, Edinburgh, 2011), p.8 47 ‘Conserve and Save’, 2009, Annexe F

19

solutions. This fact only stresses the importance of constructing the flatted

accommodation to the highest standards in the first place.

A 'Zero Carbon' home - compulsory from 2016, must also meet the Fabric

Energy Efficiency Standard (FEES). This has been set as a limit for energy

demand for space heating and cooling of 39 kWh/m2/a for flats and terraced

houses, and 46 kWh/m2/a for detached and semi-detached houses.48

A way to exceed these requirements and to come close to meeting the

‘Carbon Compliance’ element of the 'Zero Carbon' definition without additional

renewable energy devices is opting for the Passivhaus standard.49 AECB, an

independent UK-based organisation with an aim of developing sustainable

building guidance, recognises the virtues of Passivhaus by making it a

reference point for its own set of voluntary standards developed within the

CarbonLite programme.50

48 ‘Defining a Fabric Energy Efficiency Standard for Zero Carbon Homes: Task Group

Recommendations’, (Zero Carbon Hub, London, 2009), <www.zerocarbonhub.org>, [Accessed on: 1 April 2012]

49 Melissa Taylor, and Neil Cutland, ‘Passivhaus and Zero Carbon’, [Technical briefing document], (Passivhaus Trust, 2011), p.2

50 ‘AECB CarbonLite Programme: Delivering buildings with excellent energy and CO2 performance: Volume Three: The Energy Standards: Prescriptive and Performance versions’ [version 1.0.0] (Carbon Literate Design and Construction, Sustainable Building Association 2007) <http://www.aecb.net > [Accessed on: 23 February 2012]

20

1.2.2. Passivhaus Standard

1.2.2.1. Requirements / Definition

Passivhaus (PH) is a holistic approach that produces buildings in which

comfortable temperature can be achieved with minimal energy consumption51

through pre-heating or pre-cooling of the fresh air mass required to sustain

indoor air quality.52 Being more challenging compared to traditional buildings

at all stages of procurement, they require an alternative approach to design,

one that considers small details along with initial concepts.

There are around 30,000 Passivhaus buildings built since the first experiments

in Darmstadt in 1991.53 It is proven that they are generally:

Efficient, using 10% of the energy used by an average building

Quality assured to deliver proven performance

Comfortable - warm, no draughts or cold surfaces

Healthy - good internal air quality

Affordable in the long-term through reduced running costs 54

51 Dr, Wolfgang Feist, ‘Certification as "Quality approved Passive House" Criteria for

Residential-Use Passive Houses’, (Passivhaus Institut, Darmstadt, 2009) 52 Kym Mead, and Robin Brylewski, ‘Passivhaus Primer: Introduction: An Aid to Understanding

the Key Principles of the Passivhaus Standard’, (Building Research Establishment, Watford, 2011), <http://www.passivhaus.org.uk/page.jsp?id=73>, [Accessed on: 12 February 2012]

53 Ibid. 54 Taylor and Cutland, p.2

21

In return for these results, the design is required to achieve the following

criteria:

Specific Heating Demand ≤ 15 kWh/m2/a

(or) Specific Heating Load ≤ 10 W/m2

Specific Cooling Demand ≤ 15 kWh/m2/a

Specific Primary Energy Demand ≤ 120 kWh/m2/a

Air tightness ≤ 0.6 ach @ 50pascals (n50)

A way to achieve these criteria is to use the guideline targets of the building's

components’ performance as a start:

U-values for opaque fabric of ≤ 0.15 W/m2

U-values for windows and doors (frame + glazing) ≤ 0.8 W/m2K

Thermal bridging minimised (psi (y) value of < 0.01 W/m2K)

Whole house mechanical ventilation with heat recovery (MVHR)

with efficiency ≥ 75%55 and specific fan power ≤ 0.45 Wh/m3. 56

Passive House Planning Package (PHPP) software should be used to verify the

predicted performance of the design at all stages. 57 Only upon final

certification can the building claim the Passivhaus standard, provided that all

criteria are satisfied.58

55 Mead and Brylewski, p.3 56 Dr Wolfgang Feist, Passive House Planning Package, PHPP 2007, 2nd Edition, [Technical

Information PHI-2007/1 (E)], (Passive House Institute, Darmstadt, 2010), p.14 57 Passive House Institute, Passive House Planning Package 2007 [Computer Programme],

Available from BRE, <http://www.passivhaus.org.uk/page.jsp?id=25> 58 Feist, 2010, pp.24-30

22

1.2.2.2. Applicability to the Tenement

Area to Surface (A/V) ratio is used as a measure of the building's

compactness and 0.7 or less is considered favourable for Passivhaus. The A/V

ratio of the tenement as a whole is 0.38, and it is 0.49 if you consider the

common close external,59 which gives it a considerable advantage over single-

family houses.60

The common close of the tenement – either heated or not, is not considered

in Standard Assessment Procedure (SAP) calculations. 61 In contrast, only

when falling outside of the thermal envelope can it be omitted from PHPP

simulation. It saves energy to leave the stairwell out, and, due to the

compactness of apartment blocks, these unheated spaces can serve as

acceptably warm buffer zones. 62 This is the strategy proposed for the

prototype.

When a flatted block has a non-residential use, it can only be excluded if

there is sufficient thermal separation between them. Same logic applies to

buildings forming a terrace - they will also be considered as one unit, unless

59 See Appendix 6.2. for calculation 60 Rob McLeod, Kym Mead, and Mark Standen, ‘Passivhaus Primer: Designer’s Guide: A Guide

for the Design Team and Local Authorities’, (Building Research Establishment, Watford, 2011), <http://www.passivhaus.org.uk/page.jsp?id=73>, [Accessed on: 12 February 2012]

61 ‘The Government’s Standard Assessment Procedure for Energy Rating of Dwellings’, [2009 edition, version 9.90], (Building Research Establishment, Watford, 2011), p.15

62 ‘Design Guidelines: Non-Domestic Passive House Projects’, (Sustainable Energy Authority of Ireland Renewable Energy Information Office and MosArt Architecture, 2010), p.59

23

thermal resistivity of party walls is sufficient to act as a barrier.63 It is also

worth noting that, unlike SAP, which assesses individual dwellings, whole

buildings are assessed in PHPP, as flats can not be certified separately.64

There are two options for services distribution in apartment blocks -

centralised and decentralised. Although the decentralised distribution system

is more commonly used for MVHR, the alternative has its advantages if

installed in a suitable project. First, it can be centrally managed, which is

especially relevant in subsidised housing. Second, centralised positioning of

the MVHR can deliver small space savings in individual apartments. Lastly, a

central MVHR is more energy efficient, especially when the served individual

units are quite small.65

Among the disadvantages are having to deal with fire compartmentalisation

issues, sound attenuation challenges and the complexity of providing

individual controls. 66 However, all of these can be overcome, as was

demonstrated by the Mühlweg Street case study described in Chapter 3, so a

centralised MVHR system located in the attic is proposed for the prototype.

63 Mead and Brylewski, p.9 64 Feist, 2009 65 ‘Design Guidelines: Non-Domestic Passive House Projects’, p.56 66 Ibid., p.57

24

1.2.2.3. Passivhaus in the UK

In Germany, Passivhaus construction costs around 3%-8% extra compared to

conventional alternatives.67 One of the first PH projects in the UK was 14%

more expensive to construct than a house built to 2010 Building Regulations.

However, due to reduced operational expenditure and the benefits of the

feed-in tariffs, it was predicted that the payback period would be 17 years.68

This was a one-off project and did not benefit from the economies of scale.

Adopting Passivhaus in the UK is a challenge, since an average consumer

'expects central heating and wants a fireplace'.69 Among the main reasons for

the standard’s slow adoption in the UK is the strong tradition of masonry

construction, which poses challenges in terms of detailing for air-tightness

and minimisation of thermal bridges. A lack of a developed market and

suitable locally-produced building products is another reason, but it is likely to

change when the demand increases. 70 In the meantime, savings can be

achieved by simplifying building procedures and rethinking details.

67 Jon Bootland, ‘Passivhaus Principles’ , (EcoBuild presentation from Passivhaus Trust, 01

March 2011) <http://www.passivhaustrust.org.uk/UserFiles/File/Jon%20Bootland-%20Ecobuild%20Passivhaus%20Principles.pdf>, [Accessed: 11 February 2012]

68 Nick Newman, ‘Payback: Applying Passivhaus Research to the Cost-Driven World of Construction’, (Presentation from bere:architects at the Student Passivhaus Conference, 10 October 2010)

69 Isolda Strom, Loes Joosten, and Chiel Boonstra, ‘Passive House Solutions’, (Promotion of European Passive Houses, 2006), p.42

70 Strom et al., p.5

25

All buildings need to be modelled in SAP to demonstrate compliance, and

Passivhaus is no exception. Research by AECB into the differences between

PHPP and SAP highlighted the fact that SAP underestimates the benefits of

high insulation and air-tightness in low-energy houses.71 For developers eager

to obtain high environmental ratings Passivhaus might not be the most

attractive choice, as alternatives might deliver greater DER/TER percentage

reductions.

A report by the UK-based Passivhaus Trust recommends that Passivhaus-

certified dwellings are granted a "deemed-to-satisfy" status for Part L 2013.72

However, as long as Passivhaus remains unrecognised as an alternative route

to compliance, it will be up to the clients and the architects to transform the

market.

71 Liz Reason, and Alan Clarke, ‘Projecting Energy Use and CO2 Emissions from Low Energy

Buildings. A comparison of the Passivhaus Planning Package and SAP’, (AECB, 2008), <http://www.aecb.net/> [Accessed on: 1 April 2012], p.31

72 Neil Cutland, ‘Passivhaus Trust Outline Position Re. 2013 Domestic Regulations’, (Passivhaus Trust, May 2011)

26

2. Construction

2.1. Timber construction

2.1.1. Advantages

Trees absorb carbon dioxide during their growth and store it within until they

decay or are burned, making timber a highly sustainable material.

Furthermore, wood consumes 50% of the energy required to produce

concrete and 1% of that needed to produce steel.73

An estimated saving of 83% on embodied carbon emissions can be achieved

by increasing timber content in the build-up of a 4-storey block of flats

compared to traditional construction methods.74 This figure can be further

increased if timber is locally produced. Furthermore, buildings with increased

timber content are generally lighter, which alleviates pressure on foundations

and means that savings can be made by reducing their size.

73 Robert Hairstans, Off-site and Modern Methods of Timber Construction: a Sustainable

Approach, (TRADA Technology, UK, 2010), p.54 74 Jill Burnett, ‘Forestry Commission Scotland Greenhouse Gas Emissions Comparison -

Carbon Benefits of Timber in Construction’, (Edinburgh Centre for Carbon Management Ltd., Edinburgh, 2006)

27

2.1.2. Timber Construction in Scotland

Timber frame is the most common house construction system in Scotland,

accounting for 65% of the market. 75 Pre-fabricated kits are also available. A

system developed by the now defunct ‘RTC Timber Systems’ was capable of

meeting the Passivhaus standard, but was only appropriate for low-rise

housing.76

The most common structural grading for local timber is C16. Although

perfectly suitable for timber framing, it is usually avoided in favour of the

stronger (C24) imported timber, less of which is required. While there are

some supply chain issues preventing the wide-spread use of local timber, past

prejudices are the main obstacle, as it is still perceived to distort easily and to

be full of knots.77 Cutting-edge multi-storey timber construction is not about

linear elements; rather its basic unit now is a slab,78 which means that there

are ways in which Scottish timber can become highly competitive. By re-

engineering the natural product into a homogenous material improved

performance can be achieved, while also optimising the use of resources and

minimising waste.79 This might enable local timber to be used not only in

single-family houses, but in larger residential schemes as well.

75 ‘Designing Housing with Scottish Timber - a Guide for Designers, Specifiers and Clients:

Case Studies’, (John Gilbert Architects, Forestry Commission Scotland, 2005), p.3 76 ‘Pioneering Passivhaus Timber Frame Firm Falls Victim’, Timber and Sustainable Building,

15 July 2011, <http://www.timber-building.co.uk/>, [Accessed on: 2 April 2012] 77 ‘Designing Housing with Scottish Timber…’, pp.32-33 78 Andrea Deplazes, ‘Wood: Indifferent, Synthetic, Abstract - Plastic’, in (ed.) Deplazes, A.,

Constructing Architecture: Materials, Processes, Structures - a Handbook, 2nd Edition, (Birkhauser, Germany, 2010), pp.77-82, p.77

79 Hairstans, p.73

28

2.3. Modern Methods of Timber Construction

2.3.1. Applicability to Affordable Housing

In his book on the subject Robert Hairstans argues that the application of the

both efficient and effective "modern methods" to off-site timber construction

can lead to a more socially, economically and environmentally sustainable

industry, and that only a step change such as this will enable Britain to

overcome the shortage of housing.80

Within the Modern Methods of Construction (MMC) there are four product

sectors: panelised units; volumetric construction; hybrid techniques, and

other components.81 All of these construction systems offer quick erection on

site, which is not only advantageous for rural locations, where workforce is

limited, but also for urban areas - where neighbours will appreciate the

reduced noise and disruption.

To gain the numerous benefits associated with the MMC, one has to take

certain risks – such as the difficulty of absorbing late design changes, the

necessity to work to tight tolerances and the possibility of severe delays due

to problems in the supply chain.82

80 Ibid., p.10 81 Ibid., p.12 82 Ibid., p.14

29

With the increasingly individualistic society, it is important to offer variety. By

achieving a large degree of flexibility in a mass-production environment, one

can achieve mass-customisation, allowing a set number of designs to be

produced from range of standard component parts.83 This can only be cost-

effective when a large volume of houses is being built, and is especially

relevant for affordable housing. In the Passivhaus Tenement variety can be

introduced not only by removing load-bearing functions from internal walls,

but also by developing a set of fenestration alternatives.

For construction to be sustainable, it has to provide a "service", rather than a

finished "object",84 and breaking up the design into smaller components that,

in the end of the building's life, can be rearranged without losing their value

(rather than being demolished) can be an important step towards greater

environmental responsibility and towards a more flexible affordable housing

stock.

83 Ibid., p.27 84 Ibid., p.53

30

2.3.2. Engineered Timber: Cross-Laminated Panels

2.3.2.1. Properties & Features

Cross-laminated timber (CLT) is a type of MMC. It comes in panels that have

an odd number of softwood plank layers stacked on top of each other at right

angles and glued together under pressure (Fig.3). Walls, floors and roofs can

be made out of pre-fabricated panels, reducing the time on site and delivering

whole-life cost savings.85

Fig.3. Cross-Laminated Timber panel: pre-fabricated, fire resistant, air-tight86

Provided that timber comes from a certified (preferably local) source and the

glue is non-toxic, CLT can be a highly sustainable material. The Passivhaus

85‘Cross-Laminated Timber: Introduction for Specifiers’, [TRADA Wood Information Sheet,

WIS 2/3-61], (TRADA Technology, 2011) 86 Author

31

Tenement can potentially store around 70 tonnes of locked-in carbon inside

its structure, significantly reducing the carbon footprint of the project.87

Unlike masonry, which limits the building’s height and leads to heavy,

material-intensive construction,88 12-storey buildings are possible with CLT –

using 135mm internal wall, 125mm external wall and 125mm thick floor.89 In

fact, to avoid over-specification of the panels, this material has to be applied

to large-scale medium- and high-rise projects.90

The 9-storey high "Stadthaus" in London by Waugh Thistleton Architects was

the first built example of multi-storey CLT construction in the UK. Due to the

widespread lack of practical knowledge about tall timber buildings, parties

such as the National House Building Council and the Building Research

Establishment had to be employed by the CLT manufacturer to establish the

project's feasibility.91

One of the biggest challenges for the design team was overcoming the

conventional belief that timber buildings fail quicker in a fire. CLT outperforms

joists and studs by relying on the fire-retarding charring of the panels. While

87 Based on 300m3 of CLT used in the prototype and carbon storage potential found in KLH:

Sustainability, (KLH, 2012), <http://www.klhuk.com/>, [Accessed on: 9 April 2012] 88 Lehmann, p.235 89 ‘Worked Example - 12-storey Building of Cross-laminated Timber (Eurocode 5)’, (TRADA

Technology, 2009) 90 Hairstans, p.86 91 Henrietta Thompson, and Andrew Waugh, Karl-Heinz Weiss, and Mathew Wells, (eds.), A

Process Revealed / Auf dem Holzweg, (Murray & Sorrell FUEL / Thames & Hudson, Belgium, 2009), p.62

32

the three-layer lamination can deliver a fire rating of F-30, CLT used in the

"Stadthaus" had 5 layers and a rating of F-60.92

It was also important to prevent the possibility of a progressive collapse. The

panels can span in two directions and were designed to act as cantilevers

when support is removed.93

CLT has a significantly higher density than timber frame (500 kg/m3),94 which

not only provides greater thermal mass, but offers acoustic advantages as

well. Although apartments and terraces built using MMC tend to suffer from

acoustic transfer issues through party walls,95 CLT buildings have been shown

to exceed statutory requirements.96

2.3.2.2. Suitability for Passivhaus Construction

Among the requirements for Passivhaus buildings is high performance of the

building fabric – as outlined in Chapter 1.2.2. Good thermal properties of CLT

(λ = 0.13 W/mK)97 help in minimising thermal bridges and enable structural

elements to act as additional thermally resistant layers. However, unlike

conventional timber frame, wall build-ups using CLT may lead to an increase

92 Thompson et al., p.12 93 Ibid., p.77 94 Hairstans, p.14 95 Ibid., p.14 96 Thompson et al., p.34 97 ’Cross-Laminated Timber: Introduction for Specifiers’, p.8

33

in the overall thickness of the wall. Furthermore, substantial amounts of

external insulation are likely to necessitate additional framework to support it.

With a large proportion of manufacturing carried out off-site, quality control

and precision are significantly improved, which makes thermal-bridge free and

air-tight construction easier to achieve. CLT panels are air-tight on their own

and do not require additional measures except for the correct detailing of the

junctions.98 Furthermore, CLT panels are relatively easy to cut openings in

without compromising structural properties, which helps with the integration

of potentially bulky air ducts.

2.3.2.3. Procurement

Although the majority of hard work on the promotion of CLT was carried out

by the design team of the "Stadthaus", there is still an obstacle - there are no

current British or European standards for the material. These are likely to

come in 201299 and the rise in awareness and interest is expected to increase

thereafter.

The biggest producers and exporters of CLT are Austria, Switzerland and

Germany, where local smallholdings supply timber such as spruce, larch and

pine with strength gradings of C16 to C24.100 However, importing CLT is said

98 Ibid., p.8 99 Ibid., p.2 100 Ibid., p.5

34

to be expensive and, according to one of the first architects in Scotland to

have recognised the material’s potential, John Gilbert, UK manufacture is

required in order to establish a stable price appropriate to social housing.101

The type and quality of the source timber does not seem too dissimilar to

what is available locally. And it probably should not be surprising to see

activity aimed at establishing local manufacture to use up the vast amounts of

low-grade timber available. A speaker for Wood100 announced plans for

opening a factory in Scotland at a Scottish Ecological Design Association

conference in 2009. 102 Binder-Jones Ltd. is another company with similar

plans. Having started by supplying the UK industry with their version of the

product, their ultimate goal is to manufacture CLT from British-grown

wood.103 To establish the feasibility of this, structural testing of CLT from local

timber is currently being carried out by the Wood Products Innovation

Gateway at the Edinburgh Napier University.104

101 ‘Designed for Brettstapel - Scottish Housing Expo’, (Brettstapel, 2010),

<http://www.brettstapel.org/Brettstapel/Home.html>, [Accessed on: 20 March 2012] 102 Miles Montgomery cited in Balchin, A., ‘Massive Timber - Why Aren't We Using It More?’,

(Unpublished BSc dissertation, University of Strathclyde, 2009), p.9 103 Binder-Jones - Press Release (Binder-Jones, 2012) <http://www.binder-jones.co.uk/>

[Accessed on: 16 February 2012] 104 Edinburgh Napier University: Wood Products Innovation Gateway (Edinburgh Napier

University, 2012), <http://www.napier.ac.uk/ >, [Accessed on: 15 February 2012]

35

3. Case Studies

3.1. Mühlweg Street, Vienna,

Dietrich I Untertrifaller Architekten, 2006

Fig.4. External view of Mühlweg Street housing 105

3.1.1. Background to the Project

Vienna's municipal policy in the beginning of the 1920s was highly social, to

the extent that industrialised building methods were avoided in the

construction of new dwellings in favour of local craftsmanship - as it provided

more jobs.106 It seems that Austrian construction industry has maintained a

meticulous attention to detail even as the new methods of construction took

over.

105 Walter Zschokke, (ed.) Dietrich | Untertrifaller: Buildings and Projects since 2000,

(Springer Wien New York, 2008), p.210 106 Wolfgang Forster, Housing in the 20th and 21st centuries, (Prestel, Munich; London, 2006),

p.29

36

Austrian nationwide programme "Building of Tomorrow" supported research

and development in sustainable construction and provided partial grants for

the erection of demonstration projects, one of which was a housing scheme

designed by Dietrich I Untertrifaller Architekten.107 Being the first of its kind in

Europe, it required dedication on the part of all the parties involved in its

delivery.108

The scheme provides 70 affordable flats for approximately 200 residents to be

rented within four Passivhaus-certified 4-storey blocks with A/V ratio of 0.44.

Every single apartment has a flexible plan which includes an outdoor seating

area. 109

Fig.5. Typical Plan of Mühlweg Street housing 110

107 ‘10 years of the program Building of Tomorrow 1999-2009’ (Federal Ministry of Transport,

Innovation and Technology, Austria, 2009) 108 Dominique Gauzin-Muller, 'Green Building' in Zschokke, W. (ed.) Dietrich | Untertrifaller:

Buildings and Projects since 2000, (Springer Wien New York, 2008), pp.284-293, p.289 109 Ibid., p.290 110 Zschokke, p.292

37

This 6,750 m2 development was delivered at 1,065 EUR/m2 (884 £/m2)111 and

demonstrated that sustainable buildings were possible in the affordable

housing sector. 112 It was established that further environmental

improvements could have been made at little extra cost had they been

included in the original tender documents.113

3.1.2. Construction

Reinforced concrete was used to construct basements, ground floor walls and

stair cores, with the rest constructed from pre-fabricated CLT in a week’s time.

The exterior walls achieve a U-value of 0.145 W/m2K. The roof has a U-value

of 0.075 W/m2k by having 400mm of insulation on top of 146mm-thick CLT

panels. Triple-glazed windows have a U-value of 0.74 W/m2K.114

Fig.6. Detail of exterior wall of Mühlweg Street housing 115

111 At a Euro/Pound conversion rate 0.83 112 Gauzin-Muller in Zshokke, p.291 113 ‘10 years of the program Building of Tomorrow 1999-2009’ 114 Gauzin-Muller in Zshokke, p.290 115 Zschokke, p.293

38

3.1.3. Environmental Systems and Performance

All apartment blocks have an 83% efficient centralised MVHR system located

on the roof, supplying 1800 m3 of air per hour. The air is delivered at 17°C,

and all flats have small space heaters in each room. Hot and cold water

meters are located within each flat. Although each block has 60m2 of solar

hot water collectors, they are not enough to meet the total demand, so the

basement accommodates two gas tanks feeding a boiler and supplying energy

for the pre-heating of the air when the outside temperature falls to -3°C.116

The building’s annual heating demand is under 10 kWh/m2 and an air-

tightness test revealed an air exchange rate n50 below 0.3 1/h.117

The overwhelming majority of residents highly rate the quality of

accommodation and attribute this to the use of wood as a construction

material and the adherence to the Passivhaus standard.118

116 Ibid., p.290 117 Ibid., p.290 118 [Results of a survey, 2007], Ibid., p.292

39

3.2. Passivhaus and Massive Timber in the UK

Although the adoption of both Passivhaus and solid timber construction in UK

has been slow due to the reasons outlined in Chapters 1.2.2.3 and 2.3.2.3,

there are some relevant case studies to refer to. A short description is

followed by a comparative table.

Nash Terrace, Aubert Park, 4orm Architects, London

Fig.7. External view of Nash Terrace 119

This Passivhaus terrace was erected in 5 weeks using DubelHolz solid timber

panels. Each house has a double height living cube, four double bedrooms

with en suites, a cinema room, a games room and two roof terraces. Each

house collects rainwater for WCs and laundry; each has whole house MVHR

and a ground source heat pump providing heating and domestic hot water.

The annual energy bill is £80, 120 which is still unlikely to compensate for the

exuberant price charged for apartments.

119 (Nash Terrace, Aubert Park (2010) Fact Sheet. 4orm Architects. Available at:

www.4orm.co.uk (Accessed 15 March 2012) 120 Our Portfolio, (Building Research Establishment, Watford, 2012),

<http://www.passivhaus.org.uk/podpage.jsp?id=90>, [Accessed on: 12 February 2012]

40

Bridport House, Karakusevic Carson Architects, London, 2011

Fig.8. Model of the completed CLT shell of Bridport House 121

This affordable apartment block was developed for The Homes &

Communities Agency for a total budget of £6,000,000. As the building sits on

top of a sewer, care had to be taken not to overload it, so CLT was chosen for

its light weight and ability to deliver an increase in the number of units.

Engineered brick was nevertheless adopted as external finish. Structure was

built in 10 weeks and cores were also made from CLT to eliminate movement

joints. Internal walls are non-load-bearing to increase flexibility. Acoustic

performance of party elements exceeds the Building Regulations by 5dB. The

project also features a brown roof and photovoltaic panels, achieving the

Code for Sustainable Homes Level 4.122

121 Cook, S., ‘Bridport House – The Contractor’s View’ [Presentation] (Wilmott Dixon Group,

2011), <www.buildingcentre.co.uk>, [Accessed on: 1 April 2012] 122 Amanda Birch, 'Technical: Timber Structures: Bridport House', BD Online, 24 Jun 2011,

<www.bdonline.co.uk>, (pp.16-17)

41

Stadthaus, Waugh Thistleton Architects, London, 2008

Fig.9. Perspective section through the Stadthaus 123

This block of 29 apartments on a tight 17m x 17m site was the first project in

the UK to have used CLT. The challenges the design team faced are described

in Chapter 2.3.2.1. It was delivered during a 49 week period, which

compares to the estimated 72 if the building had been in concrete.124 The

designers of the "Stadthaus" exceeded acoustic requirements125 and achieved

EcoHomes “Very Good” rating.126

123 Thompson et al., p.75 124 Ibid., p.8 125 Ibid., p.34 126 Kucharek, J.C., ‘Process: Wood for the Hood’, RIBA Journal, 2010,

<http://www.ribajournal.com/>, [Accessed on: 1 April 2012]

42

Summary of Case Study Data

No of Storeys

Total area CLT No of units

Size of units m2

Affordable Case Study Year Development Erection housing

m2 time (w) ratio Mühlweg 2006 4 6,750 1x4 70 96 100% Aubert Park 2010 5 2,328* 5 8 291 0% Bridport 2011 5 - 8 4,220 12 41 103 100% Stadthaus 2009 9 2,750 9 29 95 46%

Case Study Total budget

Cost per m2

Cost per Price per Dwelling

Specific Space Heating Demand kg/m2 CO2

Dwelling

Mühlweg 5,966,663 884** 85,238 - 10 - Aubert Park - - - 2,500,000 11 - Bridport 6,000,000 1,422 146,341 - - *** Stadthaus 3,800,000 1,400127 131,034 - - 28.69128

U-value (W/m2K) Air tightness

ac/h

Air perm.

m3/h/m2 MVHR

CLT produced

by

Case Study

wall roof window Mühlweg 0.145 0.075 0.74 0.3 - 83% KLH129 Aubert Park 0.15 0.17 0.7 0.5 - - Kaufmann Bridport 0.13 0.12 1.37 - 3 - StoraEnso Stadthaus 0.27130 - - - 3 70%131 KLH

Case Study Green features & technologies / Achieved code levels

Mühlweg 60m2 of solar hot water collectors per block Aubert Park Rainwater harvesting, GSHP for heating and DHW 132 Bridport Brown roof, photovoltaic panels; Code for Sustainable Homes (CSH) Level 4. 133 Stadthaus EcoHomes Very Good

* Red denotes deduced figures; all other data comes from previously identified

sources unless noted otherwise

** Euro to Pound conversion rate - 0.83

*** A 25% reduction of DER/TER 2010 can be assumed (CSH 4)134

127 Thompson et al., p.36 128 Lowenstein, O., ‘Towering Timber’, The Architect’s Journal, 08.05.08, pp.40-42 129 ‘10 years of the program Building of Tomorrow 1999-2009’ 130 ‘Saving 120 tonnes of CO2’, Detain Green, 02/2009, (p.2) 131 ‘Stadthaus, 24 Murray Grove, London’, [Case Study], (TRADA Technology, 2009) 132 All information from: Nash Terrace, Aubert Park - Fact Sheet, (4orm Architects, 2010),

<www.4orm.co.uk>, [Accessed on: 15 March 2012] 133 All information from: Birch, 2011 134 ‘Code for Sustainable Homes: Technical Guide’ ,(Department for Communities and Local

Government, London, November 2010), p.32

43

3.3. Conclusions

All projects featured short construction time, which usually entails some

savings. Their acoustic performance typically exceeds recommended levels,

demonstrating that traditional problems with noise transfer in flats can be

minimised. 135

Typical costs vary - the only combination of Passivhaus with CLT identified in

the UK is an up-market development in central London. Apart from its

location, the high apartment prices could be attributed to the abundance of

costly green technologies and extravagant space allowances. The average

cost of affordable low-energy multi-storey accommodation made from CLT in

London is around 1,400 £/m2.

The Austrian project seems to have been heavily subsidised by manufacturers

interested in promoting the uptake of their products in schemes of this kind.

Its affordability could be replicated if similar market conditions existed in

Scotland. According to some sources, parallel tendering for the same project

revealed that the “eco-desirable” version cost only 1.9% extra.136 A factor

that contributed to the low cost of construction was the large scale of the

development.

135 Sean Smith, John B Wood, and Richard Mackenzie, ‘Housing and Sound Insulation:

Improving Existing Attached Dwellings and Designing for Conversions’, (Scottish Building Standards Agency; Historic Scotland; Communities Scotland. Arcamedia, Edinburgh, 2006), <http://www.scotland.gov.uk/Resource/Doc/217736/0099123.pdf>, [Accessed on: 16 March 2012]

136 Lehmann, p.335

44

Two of the UK projects achieved comparable environmental ratings –

EcoHomes “Very Good” and what it was later replaced with in England and

Wales – CSH Level 4. Having done this without gaining Passivhaus

certification means that the proposed prototype might even exceed these

levels if similar “green” features are used.

Unlike Mühlweg Street housing, Bridport and Stadthaus had stair and lift

cores made of CLT. This strategy is proposed for the prototype, as it avoids

movement joints but achieves sufficient fire rating. The Viennese project is

the closest to the Passivhaus Tenement in its form, so the same thickness of

CLT will be used for U-value and floor area calculations.

The case studies had different approaches to cladding. While Bridport was

faced in brick, Stadthaus used composite timber panels, and the walls of

Mühlweg Street housing were rendered. Passivhaus does not entail a pre-

defined aesthetic and all of these cladding options are possible. However, for

the Passivhaus Tenement it is suggested that rendering is used as it

minimises thermal bridging and can save an equivalent of an extra room per

tenement compared to brick veneer cladding.137

Successful schemes are the key to fostering the uptake of the material and

more case studies can be found in Lehmann, 2010.138

137 See Appendix 6.1 138 Lehmann, pp.335-346

45

4. Simulation

4.1. Description of Method & Scenarios

4.1.1. Method

In order to put the proposed Passivhaus Tenement in context, several

scenarios were selected for carrying out comparisons of their specific annual

heating demand and their Dwelling CO2 Emission Rate (DER):

1. Original tenement

2. Refurbished tenement

3. Building Standards tenement from CLT

4. Passivhaus Tenement

This study was undertaken with the help of two software applications. Even

though the author is not a certified user, best care was taken to ensure

correct data entry.

The use of Passive House Planning Package (PHPP) 139 is mandatory to

achieve PH certification. Developed to help architects and engineers optimise

the design of passive houses, it requires the input of geometric data,

occupancy and component specification in order to predict the whole building

performance.

139 Passive House Institute, Passive House Planning Package 2007 [Computer Programme],

Available from the Building Research Establishment, <http://www.passivhaus.org.uk/page.jsp?id=25>

46

FSAP 2009 140 was used to perform SAP calculations to demonstrate

compliance with the Building Standards and to determine Ene 1 and Ene 2

Credits for EcoHomes. Unlike PHPP, where the whole tenement was modelled,

an area-weighted figure was obtained from separate flat simulations.

When building in existing urban fabric, the maximum building footprint is

usually pre-determined. Therefore for the purposes of this study external

dimensions were kept constant (Fig.10),141 leaving internal floor areas and

ceiling heights to vary depending on their construction.

Fig.10. Diagram of a typical tenement with assumed external dimensions 142

140 Stroma Certification, FSAP 2009 (1.4.0.63), [Computer Programme], (2009) Available at:

<http://www.stromamembers.co.uk/SAPUser.aspxs> 141 See Appendix 6.2 for external dimensions 142 Author

47

In PHPP, the dimensions used are always the exterior dimensions of the

thermal envelope and the treated floor area required in calculations excludes

all walls. 143 In SAP, internal dimensions of walls are used and the floor area

includes the footprint of partitions.144

Fig.11. Diagram of the thermal envelope modelled in this study 145

The prototype was based on the plan of a typical pre-1919 tenement (Fig.1).

External wall thickness was assumed to be 600mm146 , and the plan was

scaled up to conform. As the unheated common stairwell was omitted from

the thermal envelope (Fig.11), the walls and doors facing the close were

considered semi-external, with a corresponding reduction factor used in

143 Feist, 2010, p.38 144 ‘The Government’s Standard Assessment Procedure for Energy Rating of Dwellings’, p.7 145 Author 146 ‘Energy Efficiency Best Practice in Housing - Scotland: Assessing U-values of existing

housing’, (Energy Saving Trust, 2004), <http://www.energysavingtrust.org.uk>, [Accessed on: 16 March 2012]

48

calculating their U-values.147 Further adjustments were made to the overall

floor and exterior wall areas to exclude the close before supplying the figures

to both SAP and PHPP.

Wall build-ups have been modelled in Dynamic Thermal Property

Calculator,148 arriving at kappa-values specific for the project and ready for

input into SAP. Taken as a whole, the values were a little above the average

thermal mass parameter. In PHPP, default values for high (Scenarios 1, 2)

and medium (3, 4) were used.

An allowance for thermal bridging in SAP was based on the total exposed

surface area, and in PHPP, lengths of geometric thermal bridges were kept

constant, with the coefficient changing according to scenario.

For the study to cover the worst-case scenario a free-standing tenement was

modelled, and in all of the SAP simulations ‘heavy’ overshadowing was

assumed. In PHPP a row of tenements was placed in front of all windows at

the minimum allowed distance of 18m, as defined by the Glasgow City

Council.149 For the same reasons, as 60% of all glazing in the tenement is

located at the front, north-facing orientation was chosen for the front façade.

147 ‘The Government’s Standard Assessment Procedure for Energy Rating of Dwellings’, p.16 148 The Concrete Centre, Dynamic Thermal Property Calculator Tool (v.1), [Computer

programme], (Developed by Arup, 2010), Available at: <http://www.concretecentre.com/> 149 ‘City Plan 2 – Development Guides Accompanying City Plan 2 – Residential’, [DG/RES1-3],

(Glasgow City Council, 2009) <http://www.glasgow.gov.uk/>, [Accessed on: 1 April 2012], p.40

49

The heating system in all scenarios was based on the one described in

Package 1, clause 6.1.2 of the Building Standards (Scotland). Individual flats

are equipped with gas boilers for space heating and have a metered supply of

hot water from a community solar hot water system, which is supplemented

by a gas boiler.

Full description of parameters used in the simulation is contained in

Appendices 6.3.-6.5.

50

4.1.2. Scenarios 1 & 2 – Original & Refurbished Tenements

U-values for external walls were taken from research outcomes by Baker150 -

1.1 W/m2K, and are more optimistic than other sources. U-value for the close

wall, 0.76 W/m2K, is an average of in-situ measurements by Baker 151

subjected to the reduction factor as described previously. U-values of the roof,

floor and windows were taken as 1.6, 0.6 and 4.8 W/m2K.152

70% of air leakage through the external skin of traditional dwellings can be

attributed to poor workmanship, rather than being intentional.153 Due to the

lack of data regarding the actual air-tightness of the original tenement, a

value of 10 m3/h*m2 at 50 Pa was assumed, which is the maximum

recommended in the Building Standards.

For Scenario 2, the original tenement was subjected to a series of

improvements that would take it closer to Package 1154, but that would not

disturb the fabric too much. Windows were replaced with double-glazed units

and draft-proofing lowered the air permeability to 7. Loft insulation helped

achieve 0.13 W/m2K and the roof was fitted with 35m2 of evacuated tube

collectors.

150 Dr. Paul Baker, ‘U-values and Traditional Buildings: In Situ Measurements and Their

Comparisons to Calculated Values’, [Historic Scotland Technical Paper 10], (Glasgow Caledonian University, 2011)

151 Baker, Table 2, p.16 152 ‘Energy Efficiency Best Practice in Housing - Scotland: Assessing U-values of existing

housing’ 153 ‘Air tightness in UK dwellings’, [BRE Information Paper: IP01/00], (Building Research

Establishment, January 2000) 154 ‘Building Standards Domestic 2011 Technical Handbook’, Clause 6.1.2

51

4.1.3. Scenario 3 - Building Standards + CLT

The ‘whole dwelling approach’ to energy use was adopted in the Building

Standards to allow greater design flexibility. It focuses on the calculated

carbon dioxide emissions (DER) not exceeding the target carbon emissions

(TER) for a ‘notional dwelling’.155

A simplified approach which avoids SAP calculations is designing the building

to one of the ‘packages’ defined in clause 6.1.2. The first ‘package’ was

selected for the purposes of this study. It specifies U-values for all building

elements, an air permeability of 7 m3/m2h, y-value of 0.08 W/m2K and glazing

solar energy transmittance of 0.63.

The thermal conductivity of insulation was set at 0.035 W/mK, which is

achievable with both conventional insulation and also more sustainable

materials. Achieving the target U-values with 96mm of CLT reduces the

thickness of external walls to 315mm. However, as the common stairwell was

outside the thermal envelope, close walls had to be treated as fire-rated,

acoustically-isolated semi-external walls, resulting in increase in their

thickness.156 A saving of 26m2 can nevertheless be made in the total floor

area compared to the original tenement.

155 Ibid. 156 See Appendix 6.6. for wall construction

52

The simplified approach was not designed to cover the worst-case scenario.

Without modifying the thickness of insulation, compliance with the Building

Standards Section 6 and a 2% reduction of DER/TER could be achieved by

increasing the g-value to 0.72, improving air permeability to 5 m3/m2h157 and

almost eliminating thermal bridging (Fig.12).

21.31

19.15(3%)

21.18

19.90

20.79

19.24(2%)

16.91(14%)

14.00

15.00

16.00

17.00

18.00

19.00

20.00

21.00

22.00

BS (Guide

lines)

(little

ove

rshad

owing

)

g-va

lue =

0.7

2

y-va

lue =

0.0

2

air p

ermea

bility =

5

Building

Stand

ards

(little

ove

rshad

owing

)

kg

/m2 /a

TER

Fig.12. Achieving Building Standards compliance in the worst case scenario: DER, TER and % Reduction 158

The tenement does not fully satisfy the Building Standards and some of the

areas in which it fails to comply are identified in Appendix 6.8.

157 This is the lowest limit before Mechanical Ventilation is required (‘Building Standards

Domestic 2011 Technical Handbook’, Clause 3.14.10) 158 Author

53

4.1.4. Scenario 4 - Building Standards + CLT + Passivhaus

As a basis for the development of the prototype, guideline specifications

described in Chapter 1.2.2.1 were taken. U-value for the roof and the

presence of solar panels were ‘inherited’ from Scenario 3. Modelling in PHPP,

assuming a total occupancy of 16 people, has demonstrated that this does

not yield a working PH159 in the worst case scenario unless the tenement is

adjacent to at least one other.

2522

11 10 9

8177

73

18

0

10

20

30

40

50

60

70

80

90

Passivhaus Tenement(Guidelines)

Adjacent to 1 Terrace

Specific Space Heating Demand (kWh/m2/a)

Heating Load (W/m2)

Specific Primary Energy Demand (kWh/m2/a)

Fig.13. Effect of terracing on PH compliance of a tenement designed to guideline specifications 160

159 See Chapter 1.2.2.1 for definition and criteria 160 Author. Specific Space Heating Demand – amount of energy needed to heat 1 m2 of a

building per year; Heating Load – maximum load on the heating system per m2; Specific Primary Energy Demand – includes DHW, Heating, Cooling, Auxiliary and Household Electricity and expresses the energy in primary units, which depends on fuel type used.

54

To ensure performance in all configurations, improvements had to be sought.

25 24 25 2320

11 11 11

81 80 78 79 79

73

23

91010

0

10

20

30

40

50

60

70

80

90

Passivhaus(Guidelines)

Higher g-value(0.68)

Better MVHREfficiency

(85%)

Lower SpecificFan Power (1)

Better Air-tightness (0.3)

Passivhaus

Specific Space Heating Demand (kWh/m2/a)

Heating Load (W/m2)

Specific Primary Energy Demand (kWh/m2/a)

Fig.14. Development of Passivhaus-compliant prototype using PHPP 161

Either the efficiency of MVHR had to be raised to the best practice standard of

85%162, or air-tightness had to be improved to 0.3 ac/h, as seen in the

Mühlweg Street scheme. A combination of improvements outlined in Fig.14

was added to the baseline specification for the Passivhaus Tenement

prototype to ensure workability at the maximum allowed U-values.

External walls ended up being 370mm thick, saving 4m2 compared to the

original construction within the same external dimensions.

161 Author 162 ‘Energy Efficient Ventilation in Dwellings – a Guide for Specifiers’, [GPG268], (Energy

Saving Trust, 2006), <http://www.energysavingtrust.org.uk>, [Accessed on: 30 March 2012]

55

Although Passivhaus demands an addition of an MVHR system, no extra

space would be required within individual flats, as the vertical riser for the

centralised distribution could be positioned in the storage cupboard. The

thickness of the floors, on the other hand, had to be increased to

accommodate air distribution ducts, which reduced the total treated volume.

56

4.2. Simulation Results & Analysis

4.2.1. Compliance Check

To check the performance of the four scenarios against the Building

Regulations, their DER was compared to TER163 and the results are presented

in Fig.15. As could be expected, the first two scenarios are far from reaching

the benchmark while the Passivhaus Tenement exceeds it.

45.42

34.84

19.24(2.4%)

14.33(24.7%)

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

45.00

50.00

Original Tenement RefurbishedTenement

Building Standards Passivhaus

kg

/m2/a

TER

Fig.15. Dwelling Emission Rate (DER), Target Emission Rate (TER) and % Reduction 164

163 values taken from FSAP 2009 164 Author

57

The DER taken from SAP was then evaluated against comparable CO2

emissions estimated by PHPP165.

45

35

1914

76

54

24

9

0

10

20

30

40

50

60

70

80

90

100

Original Tenement RefurbishedTenement

Building Standards Passivhaus

kg

/m2/a

SAP

PHPP

Fig.16. Total CO2 Emissions Equivalent (no household applications) – comparison of SAP (DER) and PHPP results 166

Research by AECB has that SAP not only underestimates the benefits of high

insulation and air-tightness in low-energy houses, as mentioned previously in

Chapter 1.2.2.3., but also underestimates the efficiency of MVHR systems.167

This is a possible explanation for the shift in value domination in the last

scenario (Fig.16).

While the Building Standards tenement could get 9 EcoHomes credits for Ene

1 category, Passivhaus could obtain at least 11.168

165 Taken from ‘PE Value’ worksheet 166 Author 167 Reason and Clarke, p.31 168 ‘EcoHomes 2006: The Environmental Rating for Homes. The Guidance 2006’, Issue 1.2,

(Building Research Establishment, Watford, April 2006), p.6

58

EcoHomes category Ene 2 credits are assigned for low heat loss

parameters 169 , and again, Passivhaus would have gained more credits

(Fig.17).

2.67

3.41

1.29(1)

0.60(2)

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

OriginalTenement

RefurbishedTenement

BuildingStandards

Passivhaus

W/m

2 K

Heat Loss Parameter

Ene 2 - 1 Credit

Ene 2 - 2 Credits

Fig.17. Heat Loss Parameter and EcoHomes Ene 2 Credits (based on SAP calculations) 170

169 Ibid., p.11 170 Author

59

4.2.2. Specific Annual Heating Demand

Due to inherent differences in the approach to internal heat gains calculations,

results from PHPP tend to be higher,171 which was confirmed in this study.

157

55

13

246

183

77

20

168

136

6345

126

0

50

100

150

200

250

300

Original Tenement RefurbishedTenement

BuildingStandards

Passivhaus

kW

h/m

2 /a

SAP PHPP FEE

Fig.18. Specific Annual Space Heating Demand and Fabric Energy Efficiency (Comparison of SAP and PHPP results) 172

Although falling short of the 39 kWh/m2/a set by the Fabric Energy Efficiency

Standard in the worst case scenario, detached north-facing Passivhaus

Tenement is able of meeting it when overshadowing is removed.

171 Paul Tuohy, and Davis Langdon LLP, ‘Benchmarking Scottish energy standards: Passive

House and CarbonLite Standards: A comparison of space heating energy demand using SAP, SBEM, and PHPP methodologies’, [Report commissioned by the Directorate for the Built Environment, Scottish Government], (ESRU, University of Strathclyde, 2009), p.20

172 Author

60

The tenement has 4 flat types and their specific annual space heating

demand varies considerably. This effect was extreme in the Passivhaus,

where mid-floor flats required less than a half of the ground or top floor flat’s

demand (Fig.19).

p p g (p yp )

64

50

49

20

8

7

1658

0 10 20 30 40 50 60 70

Ground Floor

First Floor

Second Floor

Third Floor

kWh/m2/a

Passivhaus

Building Regulations

Fig.19. Specific Annual Space Heating Demand Variations (per flat type, as modelled in SAP) 173

This discrepancy is neutralised by the centralised MVHR, spreading the cost of

heating among all the residents. Estimated increase in the non-domestic

electricity usage, mainly due to MVHR, is shown in Fig.20. Estimated annual

bills can be found in Appendix 6.7.

173 Author

61

Building S

tandard

s (PHPP)

Building S

tandard

s (SAP)

Passivh

aus (PHPP)

Passivh

aus (SAP)

1.6

77.0

1.9

55.1

2.4

20.0

9.8

12.60.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

kW

h/m

2 /a

Gas (Space Heating)

Electricity (Auxiliary)

Fig.20. Specific Annual Space Heating and Auxiliary Electricity Demand (comparison of SAP and PHPP) 174

Having ensured that the prototype works in the worst-case scenario,

orientation was changed and street width was increased from 18 to 100m to

determine potential savings. The results shown in Fig.21 indicate that

increasing the width of the street is particularly beneficial for south-facing

Passivhaus tenements, which highlights its reliance on solar gains as a source

of heat.

174 Author

62

246

183

77

20

246

182

77

19

246

183

77

20

246

183

78

20

0

50

100

150

200

250

300

Original Tenement RefurbishedTenement

Building RegulationsTenement

Passivhaus Tenement

kW

h/m

2 /aNorth-facing South-facing West-facing East-facing

241

179

73

19

240

178

72

15

244

181

75

18

244

181

75

18

0

50

100

150

200

250

300

Original Tenement RefurbishedTenement

Building RegulationsTenement

Passivhaus Tenement

kWh

/m2/a

North-facing (little overshadowing) South-facing (little overshadowing)

West-facing (little overshadowing) East-facing (little overshadowing)

Fig.21. Difference in Specific Annual Heating Demand Depending on

Orientation and Street Width (based on PHPP results) 175

175 Author

63

4.2.3. Effect of Urban Configurations

4.2.3.1. Effect of Terracing

Passivhaus Tenement was modelled adjacent to one and two other tenements,

achieving respective savings of 3 and 7 kWh/m2/a (see Fig.22). No heat loss

was assumed through party walls.

2017

9 8 7

7369

65

13

0

10

20

30

40

50

60

70

80

Passivhaus Tenement Adjacent to 1 Terrace

Specific Space Heating Demand (kWh/m2/a)

Heating Load (W/m2)

Specific Primary Energy Demand (kWh/m2/a)

Fig.22. Effect of terracing on the performance of PH Tenement (as modelled in PHPP) 176

176 Author

64

4.2.3.2. Effect of Hillside Terracing

Effects of the partially exposed party walls when the tenements are located

on a hill are presented on Fig.23. A half a storey (2.2 m) change in level was

assumed between adjacent buildings.

2017

14

9 8 8 7

7369 69

65

17

0

10

20

30

40

50

60

70

80

Passivhaus Tenement Adjacent to 1 lower Adjacent to 1 higher Hillside Terrace

Specific Space Heating Demand (kWh/m2/a)

Heating Load (W/m2)

Specific Primary Energy Demand (kWh/m2/a)

Fig.23. Effect of hillside terracing on the performance of PH Tenement (as modelled in PHPP) 177

177 Author

65

5. Discussion

The Passivhaus Tenement is an urban counterpart to sustainable single-family

housing already being developed in Glasgow. Not only is it perfectly suited to

compliment traditional tenements in the West and South of the city (where

affordable housing is in particularly high demand (1.1.2)); it could also be

constructed in areas that lack density, which is in line with the “decentralised

concentration” theory (1.1.1.).

The prototype addresses the need to provide accommodation for the growing

number of households. As the energy consumption of households does not

follow a simple geometric progression and the smaller the household, the less

energy efficient it is,178 it is of special significance that the clustering of these

smaller households delivers combined carbon savings. Smaller households

also tend to be more vulnerable to fuel poverty, 179 but the Passivhaus

Tenement is a further step towards its eradication (4.2.2.).

The Passivhaus Tenement constructed to minimum specifications outlined in

Chapter 1.2.2.1 exceeds the Building Standards but is not able to meet the

criteria required for Passivhaus certification in the worst-case scenario. Best

178 Tina Fawcett, Kevin Lane and Brenda Boardman, ‘Lower Carbon Futures for European

Households’, (Environmental Change Institute, Oxford, 2000), <www.eci.ox.ac.uk/research/energy/downloads/lowercarbonfuturereport>, [Accessed on: 11 February 2012]

179 ‘Glasgow’s Strategic Housing Investment Plan 2010/11 to 2014/15’, (Glasgow City Council, 10 November 2010), <http://www.glasgow.gov.uk>, [Accessed on: 5 April 2012], p.20

66

practice improvements introduced in Chapter 4.1.4 ensure that it not only

meets PH-criteria, but also gains a minimum of eleven credits for EcoHomes

Ene 1 and two for Ene 2. This simplifies the route to obtaining a “Very Good”

rating.

By exceeding the TER of the current Building Standards (which is a 30%

reduction on 2007 Standards) by at least 24%, the Passivhaus Tenement is in

good position to achieve the 60% reduction required by 2013 and the Fabric

Energy Efficiency Standard compulsory from 2016. It already achieves a DER

that qualifies for the Building Standard’s Silver level.

As shown in Chapter 4.2.2, even though the heating demand varies between

flats, a centralised MVHR helps redistribute solar gains and significantly cuts

down the bills. High ceilings and good natural lighting levels are maintained

even with bulky air ducts. A vertical riser could be placed in the storage

cupboard, without encroaching on the living space.

Despite the thick walls required to achieve the Passivhaus standard, the

prototype does not lose any of the floor space present in the original

tenement with identical external dimensions. However, no saving of an extra

room per tenement can be achieved unlike the alternative constructed to the

Building Standards.

67

Traditional tenement configurations found in Glasgow are also beneficial for

the annual heating bill of the residents and are worth replicating (4.2.3).

Furthermore, they may allow down-specifying the components to the

minimum (4.1.4).

Construction using CLT was found to not only be highly sustainable, but also

especially appropriate for multi-storey buildings (2.3.1.1). Its air-tightness and

thermal mass were identified as favourable for construction of low-energy

buildings (2.3.1.2). The ability of the panels to span in two directions enables

the removal of load-bearing walls from the interiors of the flats, making them

more flexible. Pre-fabrication of panels ensures quick erection on site and can

provide economies of scale. At the end of their lifecycle, tenements could be

dismantled and later reassembled in a different location or in a different

manner - this type of investment should be particularly attractive for the

affordable housing sector.

UK examples of CLT construction were found to exceed statutory acoustic

requirements (3.3). Moreover, higher levels of air-tightness proposed are not

only beneficial for energy conservation, but further contribute to noise

reduction. 180 This property might overcome previous presumptions about

flatted accommodation.

180 McMullan, R., Environmental Science in Building, Sixth Edition, (Palgrave Macmillan,

Hampshire, 2007), p.196

68

To improve the performance of the prototype, the pitch of the roof could be

changed to optimise the efficiency of the solar collectors, together with

maximising their overall area.181 Additional LZCGT could be incorporated into

the project to lower the carbon footprint even further. Some are especially

efficient when they serve multiple buildings.182 Some, like the photovoltaic

panels, can be an alternative to solar thermal collectors in reducing pay-back

time through the benefits of the Feed-In Tariffs.183

Treating the close walls as external and achieving the necessary U-values

without applying any reduction factors (4.1.1) will deliver further energy

savings and make the design more fool-proof.

When the tenement has a commercial function on ground floor, the effects of

including it in the thermal envelope and connecting it to the centralised MVHR

should be considered, as the benefits of any extra heat available might be

balanced out by additional air extraction requirements.

181 Photovoltaic Geographical Information System - PV potential estimation utility (PV GIS,

2012), <http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php#>, [Accessed on: 1 April, 2012] 182 Mansouri, S., ‘Glasgow tenements: Past, Present and a Sustainable Future?’ [Dissertation],

(Mackintosh School of Architecture, Glasgow, 2010) - looked at retrofitting exiting tenements, but the study of application of low and zero carbon generating technologies is applicable to new builds as well.

183 Tariffs payable per kWh of electricity produced, (Feed-in Tariffs, 2012), < http://www.fitariffs.co.uk/eligible/levels/>, [Accessed on: 10 April 2012]

69

Common barriers to achieving low carbon targets in the European

construction sector were identified by Musau and Deveci. 184 One of the

barriers is the split incentive - the unwillingness of owners to invest in energy

efficiency when tenants pay the bills. Even though additional government

funding is not available, if the developer is a social landlord acting in the

interest of the tenants, they may posses this will.

The lack of locally available standard solutions was also identified as a general

obstacle,185 but it is expected that with several companies already progressing

in that direction, locally-produced cross-laminated timber will soon be on the

market. However, there is no guarantee that this will dramatically decrease

the price or reduce the carbon footprint of the product. Demand needs to be

sufficient to drive the competition, foster improvement and reduce costs.

One way of increasing demand is incorporating standard details possible with

CLT into the Robust Details directory 186 , which should encourage the

product’s uptake with less adventurous practitioners. Incorporation into the

Green Guide might also be beneficial, as currently a bespoke service is

required to obtain a rating necessary for the EcoHomes assessment.187

184 Filbert Musau, and Gokay Deveci, 'From Targets to Occupied Low Carbon Homes:

Assessing the Challenges and Delivering Low Carbon Affordable Housing' [PLEA 2011, 27th International Conference on Passive and Low Energy Architecture, Louvain-la-Neuve, Belgium, 13-15 July 2011], in Bodard, M., Evrard, A. (eds.) Architecture and Sustainable Development, Volume 2., pp.261-266., p.262

185 Ibid., p.262 186 The scheme now applies to Scotland. Robust Details (2012)

<http://www.robustdetails.com/>, [Accessed on: 4 April 2012] 187 Green Guide 2008 Ratings, (Building Research Establishment, 2012),

<http://www.bre.co.uk/greenguide>, [Accessed: 6 April 2012]

70

The collaboration between GHA and City Building on the 'Glasgow House'

addresses another barrier identified in the above mentioned paper - the gap

in the skills and knowledge.188 By adopting the same approach, not only can

the design be improved through practical testing, but the skills required for its

delivery can be sustainably disseminated. If seen as a positive tool, this

should not necessarily lead to the ‘stifling of innovation’.189 The Passivhaus

Tenement could be an open-source prototype that housing associations could

develop and share, contributing to affordability through directing the savings

on the design fees to specifying better components.

Extra costs associated with high-performance components vary. Typical

increases of 10-15% were reported in Germany and Austria in the previous

decade190, with some current reports pointing to 3-8%.191 Until the demand is

high enough to lower the prices in Scotland, cost-effective improvements

could be pursued. Performance of cheaper windows can be optimised by

ensuring that wall insulation covers much of their frame.192 Air-tightness at

junctions can be achieved through the training of the builders.193 Reduction of

thermal bridging is also more a matter of careful consideration than of

significant capital investment.

188 Musau and Deveci, p.262 189 David Rudlin and Nicholas Falk, Building the 21st Century Home. The Sustainable Urban

Neighbourhood, (Architectural Press, Oxford, 1999), p.119 190 Berthold Kaufman, ‘Economics of High-Performance Houses’, in Hastings, R. and Wall, M.

(eds.) Sustainable Solar Housing. Volume 1 – Strategies and Solutions., (Earthscan, London, 2007), pp. 51-62, p.60

191 Bootland, p.26 192 Kaufmann in Hastings, p.55 193 Ibid., p.59

71

Among the additions required to bring the tenement from the Building

Standards level to Passivhaus are 1300m2 of 50mm thick insulation and an

MVHR system. Assuming a 5% increase on the base cost of £1400/m2,

ignoring the projected fuel price rise, the Renewable Heat Incentive194 and

relying on SAP calculations, the payback period would be 124 years. However,

if PHPP calculations are used, which are more optimistic on the electricity

needed to power the MVHR, only 35 years are required.195

Even though the time expectation of long-term oriented owners (such as

housing associations) is between 50-100 years,196 and 35 years is not too

inappropriate, it is the government subsidy that determines the budget of

social housing.197 The estimated £700/m2 allocated to housing associations by

the Glasgow City Council198 only covers half of the predicted costs, and even

the average actual price paid for social rented new builds in 2008/09 is

nowhere near the required figure. 199 Unless housing associations are

particularly successful at developing their assets, they are unlikely to invest in

high-performance projects as long as costs remain so high.

194 Tariff level tables, (Renewable Heat Incentive, 2012), <

http://www.rhincentive.co.uk/eligible/levels/>, [Accessed on: 10 April 2012] 195 see Appendix 6.7 for calculation 196 Holger Konig, Niklaus Kohler, et al., A Life-cycle Approach to Buildings. Principles,

Calculations, Design Tools, (Edition Detail Green Books, Munich, 2010), p.15 197 Rudlin and Falk, p.115 198 As mentioned in Chapter 1.1.2, 1 housing unit has a funding of around £76,000, and a

tenement will receive 607,400. 199 ‘Business Plan 2008/09. Better Homes, Better Lives’, (Glasgow Housing Association, 2007)

< http://www.gha.org.uk/>, [Accessed on: 3 April, 2010], p.24

72

Housing associations do however have the ability to make savings on the

purchase of land. Not only does it account for more than a half of the cost of

housing, its value tends to be the lowest in the inner city.200 This is one of the

reasons dense urban developments possible with tenements are particularly

appropriate for affordable accommodation.

Taking lifecycle costs rather than capital costs as a driver means including the

costs of operation and deconstruction, among other aspects.201 Adopting such

an approach renders the Passivhaus Tenement from cross-laminated timber a

valid prototype for sustainable future-proof housing. Affordability is ensured

by low operational costs, economies of scale possible with off-site pre-

fabrication, and by the performance of its components only slightly exceeding

the minimum recommended specification.

As long as SAP keeps underestimating the benefits of the key features of

Passivhaus, it remains unlikely that this voluntary standard will be widely

adopted. Until the market develops to offer CLT at a considerably lower price,

the uptake of this material is likely to remain slow, unless the housing

associations take it in their hands and drive the demand, reducing the costs

through wide-scale application.

200 Rudlin and Falk, pp.113, 116 201 Ibid., p.16

Bibliography ‘10 years of the program Building of Tomorrow 1999-2009’ (Federal Ministry of Transport, Innovation and Technology, Austria, 2009) About the AECB (Sustainable Building Association, Llandysul) <http://www.aecb.net/about_us.php> [Accessed on: 16 February 2012] ‘AECB CarbonLite Programme: Delivering buildings with excellent energy and CO2 performance: Volume Three: The Energy Standards: Prescriptive and Performance versions’ [version 1.0.0] (Carbon Literate Design and Construction, Sustainable Building Association 2007) <http://www.aecb.net > [Accessed on: 23 February 2012] ‘Air tightness in UK dwellings’, [BRE Information Paper: IP01/00], (Building Research Establishment, January 2000) Baker, P., ‘U-values and Traditional Buildings: In Situ Measurements and Their Comparisons to Calculated Values’, [Historic Scotland Technical Paper 10], (Glasgow Caledonian University, 2011) Balchin, A., ‘Massive Timber - Why Aren't We Using It More?’, (Unpublished BSc dissertation, University of Strathclyde, 2009) Balchin, P. and Rhoden, M., Housing Policy: An Introduction, 4th Edition, (Routledge, London, 2002) Binder-Jones - Press Release (Binder-Jones, 2012) <http://www.binder-jones.co.uk/> [Accessed on: 16 February 2012] Birch, A., 'Technical: Timber Structures: Bridport House', BD Online, 24 Jun 2011, <www.bdonline.co.uk>, (pp.16-17) ‘Building Standards Domestic 2011 Technical Handbook’, (Scottish Government, 2011) <http://www.scotland.gov.uk/Topics/Built-Environment/Building/Building-standards> [Accessed on: 16 March 2012] Burnett, J., ‘Forestry Commission Scotland Greenhouse Gas Emissions Comparison - Carbon Benefits of Timber in Construction’, (Edinburgh Centre for Carbon Management Ltd., Edinburgh, 2006) Bootland, J., ‘Passivhaus Principles’ , (EcoBuild presentation from Passivhaus Trust, 01 March 2011) <http://www.passivhaustrust.org.uk/UserFiles/File/Jon%20Bootland-%20Ecobuild%20Passivhaus%20Principles.pdf>, [Accessed: 11 February 2012]

‘BREEAM: EcoHomes’, (Building Research Establishment, 2012) <http://www.breeam.org>, [Accessed on: 8 April 2012] ‘Business Plan 2008/09. Better Homes, Better Lives’, (Glasgow Housing Association, 2007) < http://www.gha.org.uk/>, [Accessed on: 3 April, 2010] ‘City Building - Glasgow House Shortlisted for Industry Awards’ , (City Building, 16 May 2011), <http://www.citybuildingglasgow.co.uk/2011/glasgow-house-shortlisted-for-industry-awards/>, [Accessed on: 11 February 2012] ‘City Plan 2 - Part 3: Development Policies and Design Guidance’, (Glasgow City Council, 2009), <http://www.glasgow.gov.uk/>, [Accessed on: 11 February 2012] ‘City Plan 2 – Development Guides Accompanying City Plan 2 – Residential’, [DG/RES1-3], (Glasgow City Council, 2009) <http://www.glasgow.gov.uk/>, [Accessed on: 1 April 2012] ‘Code for Sustainable Homes: Technical Guide’ , (Department for Communities and Local Government, London, November 2010) Coleman, A., Utopia on Trial - Vision and Reality in Planned Housing, (Shipman, London, 1985) ‘Conserve and Save - A Consultation on the Energy Efficiency Action Plan for Scotland’, (Business, Enterprise and Energy Directorate, Scottish Government, 2009) ‘Conserve and Save - The Energy Efficiency Action Plan for Scotland - Annual Report 2010-2011’, (Scottish Government, Edinburgh, 2011) Cook, S., ‘Bridport House – The Contractor’s View’ [Presentation] (Wilmott Dixon Group, 2011), <www.buildingcentre.co.uk>, [Accessed on: 1 April 2012] ‘Cross-Laminated Timber: Introduction for Specifiers’, [TRADA Wood Information Sheet, WIS 2/3-61], (TRADA Technology, 2011) Cutland, N., ‘Passivhaus Trust Outline Position Re. 2013 Domestic Regulations’, (Passivhaus Trust, May 2011) ‘Defining a Fabric Energy Efficiency Standard for Zero Carbon Homes: Task Group Recommendations’, (Zero Carbon Hub, London, 2009), <www.zerocarbonhub.org>, [Accessed on: 1 April 2012] Deplazes, A., ‘Wood: Indifferent, Synthetic, Abstract - Plastic’, in Deplazes, A. (ed.), Constructing Architecture: Materials, Processes, Structures - a Handbook, 2nd Edition, (Birkhauser, Germany, 2010), pp.77-82

‘Design Guidelines: Non-Domestic Passive House Projects’, (Sustainable Energy Authority of Ireland Renewable Energy Information Office and MosArt Architecture, 2010) ‘Designed for Brettstapel - Scottish Housing Expo’, (Brettstapel, 2010), <http://www.brettstapel.org/Brettstapel/Home.html>, [Accessed on: 20 March 2012] ‘Designing Housing with Scottish Timber - a Guide for Designers, Specifiers and Clients: Case Studies’, (John Gilbert Architects, Forestry Commission Scotland, 2005) ‘The Development Plan for Glasgow - Main Issues Report’, (Glasgow City Council, 2011) <http://www.glasgow.gov.uk/en/Business/DevelopmentPlan/>, [Accessed on: 11 February 2012] Edinburgh Napier University: Wood Products Innovation Gateway (Edinburgh Napier University, 2012), <http://www.napier.ac.uk/forestproducts/pages/wood%20products%20innovation%20gateway.aspx>, [Accessed on: 15 February 2012] ‘EcoHomes 2006: The Environmental Rating for Homes. The Guidance 2006’, Issue 1.2, (Building Research Establishment, Watford, April 2006) ‘Energy Efficiency Best Practice in Housing - Scotland: Assessing U-values of existing housing’, (Energy Saving Trust, 2004), <http://www.energysavingtrust.org.uk>, [Accessed on: 16 March 2012] ‘Energy Efficient Ventilation in Dwellings – a Guide for Specifiers’, [GPG268], (Energy Saving Trust, 2006), <http://www.energysavingtrust.org.uk>, [Accessed on: 30 March 2012] English, J. (ed.), The Future of Council Housing, (Croom Helm, London, 1982) Fawcett T., Lane K. and Boardman B., ‘Lower Carbon Futures for European Households’, (Environmental Change Institute, Oxford, 2000), <www.eci.ox.ac.uk/research/energy/downloads/lowercarbonfuturereport>, [Accessed on: 11 February 2012] Feist, W., Passive House Planning Package, PHPP 2007, 2nd Edition, [Technical Information PHI-2007/1 (E)], (Passive House Institute, Darmstadt, 2010) Feist, W., ‘Certification as "Quality approved Passive House" Criteria for Residential-Use Passive Houses’, (Passivhaus Institut, Darmstadt, 2009) Forster, W., Housing in the 20th and 21st centuries, (Prestel, Munich; London, 2006)

Freeke, J., ‘People and Households in Glasgow. Current Estimates and Projected Changes 2008-2028. Demographic Change in Glasgow City and Neighbourhoods’, [Briefing Paper by Director of Development and Regeneration Services, 7 March 2011], (Glasgow City Council, 2011) Frey, H., Designing the City. Towards a More Sustainable Urban Form, (Spon Press, London, 1999) Gauzin-Muller, D., 'Green Building' in Zschokke, W. (ed.) Dietrich | Untertrifaller: Buildings and Projects since 2000, (Springer Wien New York, 2008), pp.284-293 Glasgow Housing Association: Homechoice, (GHA, 2009), <https://homechoice.gha.org.uk/>, [Accessed on: 16 February 2012] ‘Glasgow’s Strategic Housing Investment Plan 2010/11 to 2014/15’, (Glasgow City Council, 10 November 2010), <http://www.glasgow.gov.uk>, [Accessed on: 5 April 2012] Gilbert, J., The Tenement Handbook, (RIAS, Edinburgh, 1993) ‘The Government’s Standard Assessment Procedure for Energy Rating of Dwellings’, [2009 edition, version 9.90], (Building Research Establishment, Watford, 2011) Green Guide 2008 Ratings, (Building Research Establishment, 2012), <http://www.bre.co.uk/greenguide>, [Accessed on: 6 April 2012] Hairstans, R., Off-site and Modern Methods of Timber Construction: a Sustainable Approach, (TRADA Technology, UK, 2010) ‘Housing Stock by Tenure for Glasgow's Wards’ (Glasgow City Council, Development & Regeneration Services, 2011) <http://www.glasgow.gov.uk/en/Business/Planning_Development/PlanningPolicy/Population_Housing>, [Accessed on: 4 April 2012] Hunter, H., ‘Tenement Adaptability’, [Dissertation], (Mackintosh School of Architecture, Glasgow, 2006) Jacobs, J., The Death and Life of Great American Cities, (Modern Library ed., New York, 1993) Jephcott, P., Robinson, H., Homes in High Flats (Oliver and Boyd, Edinburgh, 1971), [cited in Coleman, A., Utopia on Trial - Vision and Reality in Planned Housing, (Shipman, London, 1985)] Kaufman, B. ‘Economics of High-Performance Houses’, in Hastings, R. and Wall, M. (eds.) Sustainable Solar Housing. Volume 1 – Strategies and Solutions., (Earthscan, London, 2007), pp. 51-62

Kennett, S., 'Huhne Says All New Homes Should Meet Passivhaus Standard', Building.co.uk, 12/10/10, <http://www.building.co.uk/5007159.article>, [Accessed on: 11 February 12] Key Facts, (Glasgow City Council, 2010) <http://www.glasgow.gov.uk/en/AboutGlasgow/Factsheets/Glasgow/KeyFacts.htm>, [Accessed on: 18 February 2012] KLH: Sustainability, (KLH, 2012), <http://www.klhuk.com/sustainability.aspx>, [Accessed on: 9 April 2012] Konig, H., Kohler, N., et al., A Life-cycle Approach to Buildings. Principles, Calculations, Design Tools, (Edition Detail Green Books, Munich, 2010) Kucharek, J.C., ‘Process: Wood for the Hood’, RIBA Journal, 2010, <http://www.ribajournal.com/>, [Accessed on: 1 April 2012] Lehmann, S., The Principles of Green Urbanism. Regenerating the Post-Industrial City, (Earthscan, London 2010) Lowenstein, O., ‘Towering Timber’, The Architect’s Journal, 08.05.08, pp.40-42 Mansouri, S., ‘Glasgow tenements: Past, Present and a Sustainable Future?’ [Dissertation], (Mackintosh School of Architecture, Glasgow, 2010) Mead, K., and Brylewski, R., ‘Passivhaus Primer: Introduction: An Aid to Understanding the Key Principles of the Passivhaus Standard’, (Building Research Establishment, Watford, 2011), <http://www.passivhaus.org.uk/page.jsp?id=73>, [Accessed on: 12 February 2012] McKenna, M., Typology Project: Tenement [A Record of Buildings in Glasgow: Volume One: October 2011], (Dress for the Weather Limited, SUST, 2011) McLeod, R., Mead, K., and Standen, M., ‘Passivhaus Primer: Designer’s Guide: A Guide for the Design Team and Local Authorities’, (Building Research Establishment, Watford, 2011), <http://www.passivhaus.org.uk/page.jsp?id=73>, [Accessed on: 12 February 2012] McMullan, R., Environmental Science in Building, Sixth Edition, (Palgrave Macmillan, Hampshire, 2007) Musau, F., and Deveci, G., 'From Targets to Occupied Low Carbon Homes: Assessing the Challenges and Delivering Low Carbon Affordable Housing' [PLEA 2011, 27th International Conference on Passive and Low Energy Architecture, Louvain-la-Neuve, Belgium, 13-15 July 2011], in Bodard, M.,

Evrard, A. (eds.) Architecture and Sustainable Development, Volume 2., pp.261-266. Nash Terrace, Aubert Park - Fact Sheet, (4orm Architects, 2010), <www.4orm.co.uk>, [Accessed on: 15 March 2012] Newman, O., Defensible Space: People and Design in the Violent City, (Architectural Press, London, 1973) Newman, N., ‘Payback: Applying Passivhaus Research to the Cost-Driven World of Construction’, (Presentation from bere:architects at the Student Passivhaus Conference, 10 October 2010) Niven, D., The Development of Housing in Scotland, (Croom Helm, London, 1979) ‘Our Corporate Strategy. The next three years (2011-2014)’, (Glasgow Housing Association, 2010) Our Portfolio, (Building Research Establishment, Watford, 2012), <http://www.passivhaus.org.uk/podpage.jsp?id=90>, [Accessed on: 12 February 2012] Passive House Institute, Passive House Planning Package 2007 [Computer Programme], Available from the Building Research Establishment, <http://www.passivhaus.org.uk/page.jsp?id=25> Photovoltaic Geographical Information System - PV potential estimation utility (PV GIS, 2012), <http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php#>, [Accessed on: 1 April, 2012] ‘Pioneering Passivhaus Timber Frame Firm Falls Victim’, Timber and Sustainable Building, 15 July 2011, <http://www.timber-building.co.uk/>, [Accessed on: 2 April 2012] Reason, L., and Clarke, A., ‘Projecting Energy Use and CO2 Emissions from Low Energy Buildings. A comparison of the Passivhaus Planning Package and SAP’, (AECB, 2008), <http://www.aecb.net/> [Accessed on: 1 April 2012] Robust Details (2012) <http://www.robustdetails.com/>, [Accessed on: 4 April 2012] Rudlin, D. and Falk, N., Building the 21st Century Home. The Sustainable Urban Neighbourhood, (Architectural Press, Oxford, 1999) ‘Saving 120 tonnes of CO2’, Detain Green, 02/2009, (p.2) Smith, S., Wood, J.B. and Mackenzie, R., ‘Housing and Sound Insulation: Improving Existing Attached Dwellings and Designing for Conversions’,

(Scottish Building Standards Agency; Historic Scotland; Communities Scotland. Arcamedia, Edinburgh, 2006), <http://www.scotland.gov.uk/Resource/Doc/217736/0099123.pdf>, [Accessed on: 16 March 2012] Sneddon, J., ‘The Glasgow House - It's Already Happening’, (Glasgow Housing Association, 2010) ‘Stadthaus, 24 Murray Grove, London’, [Case Study], (TRADA Technology, 2009) Strom, I., Joosten, L., and Boonstra, C., ‘Passive House Solutions’, (Promotion of European Passive Houses, 2006) Stroma Certification, FSAP 2009 (1.4.0.63), [Computer Programme], (2009) Available at: <http://www.stromamembers.co.uk/SAPUser.aspx> Sullivan, L., ‘A Low Carbon Building Standards Strategy For Scotland’, [Report of a panel appointed by Scottish Ministers], (Chaired by Lynne Sullivan from Scottish Building Standards Agency (SBSA), 2007) Tariff level tables, (Renewable Heat Incentive, 2012), < http://www.rhincentive.co.uk/eligible/levels/>, [Accessed on: 10 April 2012] Tariffs payable per kWh of electricity produced, (Feed-in Tariffs, 2012), < http://www.fitariffs.co.uk/eligible/levels/>, [Accessed on: 10 April 2012] Taylor, M., and Cutland, N., ‘Passivhaus and Zero Carbon’, [Technical briefing document], (Passivhaus Trust, 2011) The Concrete Centre, Dynamic Thermal Property Calculator Tool (v.1), [Computer programme], (Developed by Arup, 2010), Available at: <http://www.concretecentre.com/> Thompson, H. and Waugh, A., Weiss, K., and Wells, M. (eds.), A Process Revealed / Auf dem Holzweg, (Murray & Sorrell FUEL / Thames & Hudson, Belgium, 2009) Trotter, N.M., ‘The revival of the tenement tradition in Glasgow’, [Dissertation], (Mackintosh School of Architecture, Glasgow, 1996) Tuohy, P. and Davis Langdon LLP, ‘Benchmarking Scottish energy standards: Passive House and CarbonLite Standards: A comparison of space heating energy demand using SAP, SBEM, and PHPP methodologies’, [Report commissioned by the Directorate for the Built Environment, Scottish Government], (ESRU, University of Strathclyde, 2009)

Worsdall, F., The Tenement : A Way of Life : a Social, Historical and Architectural Study of Housing in Glasgow, (W. and R. Chambers, Edinburgh, 1979) ‘Worked Example - 12-storey Building of Cross-laminated Timber (Eurocode 5)’, (TRADA Technology, 2009) Zschokke, W. (ed.) Dietrich | Untertrifaller: Buildings and Projects since 2000, (Springer Wien New York, 2008)

Appendices 6.1. Effect of Wall Thickness on Total Treated Floor Area 6.2. External Dimensions 6.3. Description of Scenarios (PHPP) 6.4. Description of Scenarios (SAP – Geometry of Flats)

6.4.1. Ground Floor Flat 6.4.2. First Floor Flat 6.4.3. Second Floor Flat 6.4.4. Third Floor Flat

6.5. Description of Scenarios (SAP – Common Parameters) 6.6. Wall Construction

6.6.1. Scenario 3 – Building Standards 6.6.2. Scenario 4 – Passivhaus

6.7. Extra Costs Calculation 6.8. Building Standards Compliance of the Tenement

6.1 Effect of Wall Thickness on Total Treated Floor Area Three cladding options were investigated for the new-build prototype –

rendering, rain-screen cladding and brickwork – based on the case studies

described.

As rain-screen panels and brickwork require considerably more anchors to tie

them back to primary structure and take up more space, they are less

efficient than the alternative. Furthermore, a space equivalent of an extra

room can be saved per tenement if brickwork is replaced by render.

U value = 0.19 Rendered Rain-screen Brickwork

Wall thickness (mm) 0.315 0.355 0.44

Treated Floor Area (m2) 705.17 696.62 678.53

Difference with Rendered n/a 8.55 26.64

U value = 0.15 Rendered Rain-screen Brickwork

Wall thickness (mm) 0.37 0.405 0.485

Treated Floor Area (m2) 689.73 682.28 665.42

Difference with Rendered n/a 7.45 24.31

The comparison of the treated floor area achievable for the two scenarios

6.2 External Dimensions Wall height - front (m) 17.6 Wall height - rear (m) 17.8

Roof surface area (pitched) (m2) 267.93 Roof pitch (degrees) 30.00

External Wall - Side (1 of 2) (m2) 248.69

External Wall - Side - top triangle (1 of 2) (m2) 28.07

Stairwell within thermal envelope? Yes No

External Wall (Front) (m2) 304.00 299.39

Opening area (m2) 64.15 64.15

External Wall (Front) - excl. openings (m2) 239.85 235.24 Opening/façade ratio 21.10% 21.43%

External Wall (Back) (m2) 289.00 239.94

Opening area (m2) 57.54 42.78

External Wall (Back) - excl. openings (m2) 231.46 197.16 Opening/façade ratio 19.91% 17.83%

Footprint - Roof level (m2) 232.49 214.58

Footprint - Foundation level (m2) 232.49 205.12

Gross volume (excl. cold roof space) (m3) 4091.82 3610.11 Surface to volume ratio 0.38 0.49 Perimeter - Roof level - external (m) 61.75 57.75 Perimeter - Roof level - total (m) 61.75 74.83 Perimeter - Foundation level - external (m) 61.75 57.75 Perimeter - Foundation level - total (m) 61.75 87.48

Close wall (Average) (1 of 2) (m2) x 137.00

Opening area (m2) x 14.80

Close wall (1 of 2) excl. openings (m2) x 122.20

Close wall (Back) (m2) x 41.88

Close soffit (Corridor) (m2) x 8.77

Total external envelope area (incl. pitched roof) (m2): 1646.94

Total close wall area (m2): 324.65

Total thermal envelope area (m2): 1555.36 1781.06

6.3 Description of Scenarios (PHPP)

Original Tenementlittle

overshadowing

Refurbished Tenement

little overshad

owing

Building Standards

(Guidelines)

little overshad

owingg-value

thermal bridges

air tightness

Building Standard

s

little overshad

owing

Passivhaus Tenement (Guidelines)

little overshad

owingg-value

MVHR Efficiency

MVHR Specific

FP

air tightness

Passivhaus

Tenement

little overshad

owing

Spec. capacity (Wh/m2K) 204 - 132 -

DIMENSIONS

Treated Floor Area (PHPP) 685 - 705.17 689.73Average Height (PHPP) 3.95 - 4.03 3.8

Gross volume (m3) 3610.112 - - -Internal volume (m3) 2705.75 2841.84 2620.97

Number of occupants (design): 16 - - -

OPAQUE ELEMENTSExternal Ground Floor

(Slab on Grade, depth 0.3m) Ground type: silt/clay

Area (PHPP) 205.12 - - -Floor Slab Perimeter (external) 57.75 - - -

U-value 0.6 - 0.19 0.15Front

Area (PHPP) 299.39 299.29 299.57U-value 1.1 - 0.19 0.15

Thickness (m) 0.6 - 0.315 0.37Rear

Area (PHPP) 239.94 239.94 239.94U-value 1.1 - 0.19 0.15

Thickness (m) 0.6 - 0.315 0.37Sides

1/2 Area (PHPP) 248.69 248.69 248.69U-value 1.1 - 0.19 0.15

Thickness (m) 0.6 0.315 0.37Close: side 1 (out of 2)

Area (PHPP) 132.29 139.01 136.17U-value 0.76 - 0.19 0.15

Thickness (m) 0.25 0.35 0.4Close: back wall

Area (PHPP) 41.88 - - -U-value 0.76 - 0.19 0.15

Thickness (m) 0.25 0.35 0.4Close: soffit

Area 8.77 - - -U-value 0.76 - 0.19 0.15

RoofArea (PHPP) 214.58 - - -

U-value 1.2 0.13 - -

THERMAL BRIDGESy-value 0.15 - 0.08 0.02 0.02 0.02 0.01

Perimeter (ground) 57.75 - - -Floor Slab (close walls) 27.34 - - -

Perimeter (roof) 57.75 - - -External corners 70.4 - - -

OPENINGSDoors

U-value 1.4 - - 0.8Area 8x 1.85 - - -

Total Area 14.8 - - -Windows

Transmittance factor 'g' 0.85 0.63 - 0.72 0.72 0.72 0.5 0.68 0.68 0.68U-value 4.8 1.5 - 0.8

Shading22m at gable level

25 m away22; 100

-22; 100

-22; 100 22; 100

-22; 100 22; 100

Depth of reveal 0.15 - - -Frame dimensions (m) 0.14 - - -

y-value glazing edge 0.045 0.04 - 0.035y-value installation 0.15 0.08 - 0.02 0.02 0.02 0.01

North-facingBay-middle 8x 2.92 - - -Bay-side 1 8x 1.19 - - -Bay-side 2 8x 1.19 - - -

Bedroom 8x 2.69 - - -South-facing

Kitchen 8x 3.49 - - -Bathroom 8x 1.9 - - -

VENTILATIONVentilation Natural - - MVHRSpecific Fan Power W/l/s 1.5 1 1 1Electric Efficiency Wh/m3 0.41 0.27 0.27 0.27Heat Recovery Efficiency 75% 85 85 85Ducting type flexibleDuct insulation insulatedAir change rate at pressure test ac/h @ 50 Pa 6.3 4.4 - 3.14 3.14 3.14 0.6 0.3 0.3 0.3

HEATINGType Mains gas boiler - - -Efficiency (SEDBUK 2005) 90.20% - - -

WATER HEATINGHot Water System From main heating - - -

Cylinder volume 150 l - - -Insulation thickness 70 mm - - -

Average Heat Released (W) 72 - - -Length of distribution pipes 16 - - -

Length of individual pipes 16 - - -Y-Value W/mK 0.18 - - -

Solar Hot Water - evacuated tube - -Area of collector - 35 - -

Orientation - South - -Tilt - 30 - -

Overshading - 80% 100% - 100% 100% - 100% 100%Height of the collector field - 0.01 - -

Separate Storage volume - 200 l - -Losses W/K - 3 - -

Storage room temperature - 15 - -

SUMMER VENTILATIONWindows open half the time - - -Nighttime ventilation yes - - -

Low energy lights 3.1% 100% - -

ELECTRICITYCooking with: gas - - -

Clothes washing DHW connection - - -Clothes drying: clothes line - - -

6.4 Description of Scenarios (SAP – Geometry of Flats) 6.4.1 Ground Floor Flat

Diagram of Ground Floor Flat

6.4.2 First Floor Flat

6.4.3 Second Floor Flat

6.4.4 Third Floor Flat

6.5 Description of Scenarios (SAP – Common Parameters)

Assessment type New Dwelling Design Stage

Original Tenementlittle

overshadowing

Refurbished Tenement

little overshad

owing

Building Standards

(Guidelines)

little overshad

owingg-value

thermal bridges

air tightness

Building Standards

little overshad

owing

Passivhaus Tenement (Guidelines)

little overshad

owingg-value

MVHR Efficiency

MVHR Specific

FP

air tightness

Passivhaus Tenement

little overshad

owingThermal mass parameter Calculated - - -

DIMENSIONSTotal living area (m2) 26.4 - 28.15 27.5Height (m) 1 3.95 - 4.03 3.8

OPAQUE ELEMENTSSide

Area 51.03 - 54.41 50.88U-value 1.1 - 0.19 0.15

Thickness (m) 0.6 - 0.315 0.37Kappa 180 - 65 -

THERMAL BRIDGESy-value 0.15 - 0.08 0.02 0.02 0.02 0.01

OPENINGSDoors

U-value 1.4 - - 0.8Area 1x 1.85 - - -

WindowsTransmittance factor 'g' 0.85 0.63 - 0.72 0.72 0.72 0.5 0.68 0.68 0.68

Frame factor 'FF' 0.7 - - -U-value 4.8 1.5 - 0.8

Overshading heavy little - little - little little heavy little little

North-facingBay-middle 8x 2.92 - - -Bay-side 1 8x 1.19 - - -Bay-side 2 8x 1.19 - - -

Bedroom 8x 2.69 - - -South-facing

Kitchen 8x 3.49 - - -Bathroom 8x 1.9 - - -

VENTILATIONVentilation Natural - - MVHRSpecific Fan Power W/l/s 1.5 1 1 1Heat Recovery Efficiency 75% 85 85 85Ducting type flexibleDuct insulation insulatedWet rooms excl. kitchen 8Design air permeability m3/h/m2 @ 50 Pa 10 7 -

5 5 5 0.88 0.44 0.44 0.44

HEATINGType Mains gas boiler - - -Distribution Radiators - - -

Controls

Programmer, Room Thermostat, TRVs; user delayed start - -

-

Tariff Standard - - -Efficiency (SEDBUK 2005) 90.20% - - -Pump in heated space - - -Boiler interlock yes - - -Flue type room sealed - - -Fan-flued yes - - -Weather compensator yes - - -

WATER HEATINGHot Water System From main heating - - -

Cylinder volume 150 l - - -Insulation thickness 70 mm - - -

Storage losses KWh/day 1.73 - - -Cylinder in heated space yes - - -Cylinderstat yes - - -Primary pipework insulated yes - - -Water heating timed separately yes - - -

Solar Hot Water - evacuated tube - -Area of collector - 4.38 - -

Orientation - South - -Tilt - 30 - -

Overshading - heavy little - little little - little littleSeparate Storage volume - 200 l - -

Heat loss coefficient - 3 - -Dedicated solar store - yes - -

Solar pump - yes - -Zero-loss collector efficiency - 0.6 - -

SUMMER VENTILATIONWindows open half the time - - -Nighttime ventilation yes - - -Effective ach 3 - - -

Low energy lights 3.1% 100% - -

6.6 Wall Construction 6.6.1 Scenario 3 – Building Standards

* Adjustment:

R=0.82 U1=0.227 U2=1 / ( (1/U1)+R)= 0.19

6.6.1 Scenario 4 – Passivhaus

Internal Party Wall is identical to Scenario 3.

* Adjustment:

R=0.82 U1=0.172 U2=1 / ( (1/U1)+R)= 0.15

6.7 Extra Costs Calculation

Technical data of building Building

Standards Passivhaus Passivhaus Passivhaus

(+5%) (+10%) (+15%) Based on: PHPP

Heating demand (kWh/m²a) 77 20 20 20 Aux. Electricity demand (kWh/m²a)

1.6 2.4 2.4 2.4

Energy saving potential (kWh/m²a)

- 57 57 57

Floor area of development (m²) 930 930 930 930 Floor area of dwellings (m²) 720 720 720 720 Total annual heating demand (kWh/a)

55,440 14,400 14,400 14,400

Total annual electricity demand (kWh/a)

1,152 1,728 1,728 1,728

Total annual heating demand per flat (kWh/a/flat)

6,930 1,800 1,800 1,800

Total annual aux. electricity demand per flat (kWh/a/flat)

144 216 216 216

Total annual heating cost per flat (£ / a / flat)

256 67 67 67

Total annual aux. electricity cost per flat (£ / a / flat)

19 28 28 28

Total bill/flat 275 95 95 95 Energy saving potential (kWh/a)

- 40,464 40,464 40,464

Cost saving potential (£ / a) - 1443.6 1443.6 1443.6 Cost saving potential per flat (£ / a / flat)

- 180 180 180

Percentage saving on annual bill

- 70.38% 70.38% 70.38%

Basic building costs (£ / m²) 1400 1400 1400 1400 Extra costs % - 5% 10% 15% Extra costs (£ / m²) - 70 140 210 Total basic construction costs (£)

1,302,000 1,302,000 1,302,000 1,302,000

Total extra costs (£) - 50,400 100,800 151,200 Total costs (£) 1,302,000 1,352,400 1,402,800 1,453,200 Years to get pay-back - 35 70 105

Technical data of building Building

Standards Passivhaus Passivhaus Passivhaus

(+5%) (+10%) (+15%) Based on: SAP

Heating demand (kWh/m²a) 55 12 12 12 Aux. Electricity demand (kWh/m²a)

1.9 9.8 9.8 9.8

Energy saving potential (kWh/m²a)

- 43 43 43

Floor area of development (m²) 930 930 930 930 Floor area of dwellings (m²) 720 720 720 720 Total annual heating demand (kWh/a)

39,600 8,640 8,640 8,640

Total annual electricity demand (kWh/a)

1,368 7,056 7,056 7,056

Total annual heating demand per flat (kWh/a/flat)

4,950 1,080 1,080 1,080

Total annual aux. electricity demand per flat (kWh/a/flat)

171 882 882 882

Total annual heating cost per flat (£ / a / flat)

183 40 40 40

Total annual aux. electricity cost per flat (£ / a / flat)

22 115 115 115

Total bill/flat 205 155 155 155 Energy saving potential (kWh/a)

- 25,272 25,272 25,272

Cost saving potential (£ / a) - 406.08 406.08 406.08 Cost saving potential per flat (£ / a / flat)

- 51 51 51

Percentage saving on annual bill

- 27.71% 27.71% 27.71%

Basic building costs (£ / m²) 1400 1400 1400 1400 Extra costs % - 5% 10% 15% Extra costs (£ / m²) - 70 140 210 Total basic construction costs (£)

1,302,000 1,302,000 1,302,000 1,302,000

Total extra costs (£) - 50,400 100,800 151,200 Total costs (£) 1,302,000 1,352,400 1,402,800 1,453,200 Years to get pay-back - 124 248 372

6.8. Building Standards Compliance of the Tenement According to the Building Standards, buildings with dwelling floor levels above

10m should be provided with a lift. 1 The 3rd floor level in the studied

prototype is at 13.23m. If the lift is to be avoided, the best solution would be

to change the number of storeys to 3 so as to maintain the generous ceiling

heights and high day-lighting levels 2 , which are necessary not only for

comfort, but for obtaining extra EcoHomes credits as well.

When it comes to ground floor accessibility, some further modifications would

have to be made. Access to the back court lies under the staircase and

sufficient headroom is ensured by stepping down, which contravenes

standard 4.2. With a new corridor taking up the space of the bathroom, the

affected ground floor flat could be remodelled to provide enhanced

accessibility facilities.

1 ‘Building Standards Domestic 2011 Technical Handbook’, Clause 4.2.5 2 Hunter, H., ‘Tenement Adaptability’, [Dissertation], (Mackintosh School of Architecture, Glasgow, 2006), p.41